LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 


Class 


PRINCIPLES 


OF 


CHEMISTRY; 

EMBRACING   THK  MOST 

RECENT  DISCOVERIES  IN  THE  SCIENCE, 

AND 

THE   OUTLINES    OF   ITS    APPLICATION   TO    AGRICULTURE 
AND  THE  ARTS. 

X 

ILLUSTRATED  BY  NUMEROUS  EXPERIMENTS, 

NWWLY     ADAPTED     TO     THE     SIMPLEST     APPARATUS. 


BY  JOHN  A.  PORTER,  M.A.,  M.D. 

PROFESSOR   OF   AGRICULTURAL   AND   ORGANIC  CHEMISTRY   IN   YALE  COLLEGE. 


NEW  YORK: 

A.  S.  BARNES  &  CO.,  51  &  53  JOHN-STREET, 
I860. 

* 


Entered  according  to  Act  of  Congress  in  the  year  1856,  by 

JOHN  A.  PORTER, 

in  the  Clerk's    Office  of  the  District  Court  for  the  District  of  Con- 
necticut. 


IN  the  preparation  of  this  text-book  on  Chemistry,  it  has 
been  the  design  of  the  author  to  disencumber  the  subject 
of  much  detail,  which  is  only  of  interest  to  the  professional 
chemist,  and  at  the  same  time  to  bring  the  illustration  of  the 
more  important  phenomena  of  the  science  within  the  reach 
of  every  school  and  every  individual  student. 

The  most  distinguished  philosophers  have  not  deemed  it 
beneath  their  dignity  to  employ  the  simplest  means  of  inves- 
tigation. The  teacher  will  not  be  loth  to  take  advantage  of 
similar  means  in  illustrating  their  discoveries.  An  important 
design  of  this  work  is  to  show  how  this  object  may  be  ac- 
complished, by  the  simple  addition  of  a  few  test-tubes  and  a 
spirit  lamp,  to  a  list  of  chemical  apparatus  which  may  be 
found  in  every  house. 

Among  the  other  distinctive  features  of  the  work,  are  a 
more  complete  classification  than  usual  according  to  chemi- 
cal analogies,  the  explanation  of  chemical  phenomena  in 
ordinary  language,  as  well  as  symbols,  and  the  addition  of 
a  complete  set  of  formulae  in  the  Appendix.  A  number  of 
recent  and  important  discoveries  are  introduced,  and  the 
relations  of  Chemistry  to  the  Arts  and  Agriculture,  are  es- 
pecially considered. 

The  method  adopted  for  the  explanation  of  chemical  phe- 
nomena, while  it  is  believed  to  be  more  effectual  in  imparting 
the  leading  idea  of  all  chemical  reactions,  leaves  to  the 

1 


11  PREFACE. 

student  the  useful  exercise  of  constructing  formulae.  He 
is  at  the  same  time  supplied  in  the  Appendix  with  a  com- 
plete control  of  his  results.  This  part  of  the  work  contains 
in  addition,  numerous  tables,  and  other  supplementary  mat- 
ter  for  the  use  of  the  more  advanced  student 

The  language  of  the  atomic  theory  has  been  rigorously 
adhered  to  throughout  the  work,  as  the  best  expression 
of  our  present  knowledge  of  the  constitution  of  matter. 
While  it  is  liable  to  no  objection  which  does  not  hold  against 
the  language  of  every  department  of  Physics,  its  uniform 
employment  has  the  great  advantage  of  accustoming  the  mind 
to  a  conception  which  furnishes  a  probable  explanation  of  the 
most  obscure  portions  of  the  science. 

Several  topics  introduced  in  the  chapters  on  Physics,  are 
designed  simply  as  introductory  to  other  subjects,  and  are 
very  briefly  treated,  in  accordance  with  this  design. 

Among  the  numerous  authorities  consulted  in  the  prepa- 
ration of  this  work,  the  author  would  especially  mention  the 
works  of  Berzelius,  Liebig,  Gmelin,  Gregory,  Regnault, 
Payen,  Graham,  Silliman  and  Stockhardt.  He  would  also 
take  this  opportunity  of  acknowledging  the  important  aid 
extended  by  his  able  professional  assistant,  DR.  ROBERT  A. 
FISHER,  both  in  the  execution  of  his  design  for  a  simplified 
course  of  experiment,  and  for  valuable  information  in  rela- 
tion to  several  processes  of  applied  chemistry. 

Boxes  containing  apparatus  and  materials  neatly  put  up  to  accom- 
pany this  work,  may  be  ordered  of  J.  R  LTJHME,  &  Co.,  dealers  in 
Chemical  Apparatus  and  Pure  Chemicals,  No.  556  Broadway,  New 
York.  Price  $6.00. 

The  list  embraces  all  the  articles  named  on  the  last  page  of  the  work, 
with  the  exception  of  those  marked  with  an  asterisk,  which  may  be 
procured  of  any  druggist. 


TABLE  OF  CONTENTS. 


PART  I. 

PHYSICS. 


PAGE 

ATOMS  AND  ATTRACTION,  ...  11 
LIGHT. — Chemical     action    of 

Light, 15 

Theories, 15 

Laws,      ......  17 

Analysis  of  Light,       .     .  22 

HEAT. — Nature  and  Sources,  25 

Communication  of  Heat,  30 

Changes  effected  by  Heat,  48 


HEAT.  —  Expansion, 


PAGE 

....  50 

....  61 

Vaporization,     ....  66 

Boiling,  ......  77 

ELECTRICITY  AND  MAGNETISM,  .  99 

Galvanism,  .....  103 

Batteries,  ......  114 

Galvanic  Decomposition,  117 
Magnetic  Telegraph,  .     .124 


PART  II. 


CHEMICAL  PHILOSOPHY. 


ELEMENTS,    . 
MIC  CONSTITUTION,    . 
EXPLANATION  OF  SYMBOLS, 
LAWS  OF  COMBINATION,  .     , 


PAGE 
.  129 

129 
.  132 

134 


PAGE 

PROPERTIES  OF  ACIDS  AND  BASES,  137 
EFFECT  OF  SOLUTION,  .  .  .  138 
ELECTRICAL  CONDITION  OF  THE 

ELEMENTS, 138 


IV 


CONTENTS. 


PART  III. 

INORGANIC  CHEMISTRY. 


FAQE 

METALLOIDS. 

Oxygen, 141 

^.Ghlorine, 149 

/Modine, 156 

Bromine, 158 

-^'.--Fluorine, 158 

/      Sulphur, 159 

Nitrogen, 169 

Phosphorus,        .     .     .     .176 

Arsenic, 179 

Carbon, 185 

Boron, 197 

METALS. — Classification,  .  .231 
CLASS  I. — Potassium,  &c.  233 
CLASS  II. — Barium,  <fec.  .  237 


PAGE 

METALS. 

CLASS  III— Iron,  &c.  .  240 
CLASS  IV. — Tin,  &c.  .  243 
CLASS  V.— Bismuth,  &c.  259 
CLASS  VI. — Mercury,  <fec.  258 
SOLUTION  AND  CEYSTALIZATION,  274 
Precipitation,  ....  275 
Variety  of  Crystals,  .  279 
Forms  of  Crystals,  .  .  280 
Isomorphism,  ....  284 

OXIDES, 285 

CHLORIDES,        294 

SALTS, 300 

THE  DAGUERREOTYPE,   .  .  .327 
CHEMICAL  ANALYSIS,   .  .  .332 


PART  IV. 


ORGANIC  CHEMISTRY. 


GENERAL  VIEWS 335 

VEGETABLE  CHEMISTRY,      .     .     345 

Wood, 349 

Starch, 357 

Sugar, 359 

Alcohol, 362 

Organic  Acids,  .     .  372 

Essential  Oils,  .  .  .  379 
Artificial  Essences,  .  .382 
Resins,  ....  ,  383 


PAGE 

VEGETABLE  CHEMISTRY. 

Protein  Bodies,  ....  388 
Organic  Bases,  .  .  .  395 
Coloring  Matters,  .  .  .  3*96  < 

Dyeing, 397 

Calico  Printing,  .  .  .  400 
AGRICULTURAL  CHEMISTRY,  .  402 
ANIMAL  CHEMISTRY,  .  .  .  .413 
ORGANIC  ANALYSIS,  .  .  .  .  430 
CIRCULATION  OF  MATTER,  .  433 


IISTTRODUOTION. 


ACCORDING  to  the  most  ancient  view  of  the  constitu- 
tion of  matter,  the  earth  and  all  material  things  are  but 
modifications  of  one  and  the  same  original  substance. 
Fire,  water,  and  air,  were  each  in  turn  asserted  to  be 
the  primitive  element,  according  to  the  arbitrary  con- 
jecture of  philosophers  who  were  bold  enough  to  spec- 
ulate upon  the  subject.  At  a  later  date,  the  views  of 
all  seemed  to  be  harmonized  in  ascribing  the  same 
dignity  to  the  three  contending  elements,  and  including 
earth  among  the  original  varieties  of  matter.  Earth, 
Air,  Fire,  and  Water,  were  assumed  to  be  the  original 
materials  out  of  which  all  forms  of  matter  are  produced. 

Modern  chemistry  has  dethroned  each  of  these  ele- 
mental monarchs  of  the  world,  and  distributed  their 
prerogatives  among  a  larger  number.  Earth,  air,  and 
water,  are  all  excluded  from  the  list  of  elements,  and 


6  INTRODUCTION. 

fire  appears  in  the  modern  view  as  only  the  transient 
attendant  of  chemical  combination. 

Each  one  of  the  acknowledged  elements  has  its  own 
specific  properties,  affinities,  and  capacity  of  combina- 
tion. These  peculiarities,  and  all  resulting  phenomena, 
it  is  the  province  of  chemistry  to  investigate  and  ex- 
plain. Light,  heat,  and  electricity,  stand  in  intimate 
relation  to  all  chemical  action,  either  as  cause  or  effect, 
or  unfailing  attendant,  and  are  therefore  briefly  consid- 
ered in  the  earlier  part  of  the  present  work. 

The  study  of  science  has  not  for  its  object  the  mere 
gratification  of  an  idle  curiosity.  Looking  at  the  sub- 
ject from  a  material  point  of  view  alone,  chemistry  is 
one  of  the  great  agents  in  the  transformation  of  nature, 
and  its  subjugation  to  the  wants  of  man.  The  earth 
yields  her  treasure  to  its  skillfully  conducted  processes, 
and  even  the  trodden  clay  becomes  converted  in  its 
crucible  into  shining  metal.  The  arts  draw  from  it, 
with  every  succeeding  year,  increased  advantage,  and 
the  condition  of  mankind  is  elevated,  and  the  world 
advanced  by  its  progressive  triumphs.  Agriculture 
also  is  indebted  to  its  discoveries.  It  opens  to  us  mines 
of  agricultural  wealth  in  what  would  otherwise  have 
passed  for  worthless  refuse.  It  clothes  exhausted  fields 
with  new  fertility,  by  the  addition  of  some  failing  con- 
stituent whose  absence  its  subtle  processes  have  de- 
tected. It  carefully  investigates  the  laws  and  condi- 


INTRODUCTION.  7 

tions  of  vegetable  growth,  by  which  earth  and  air  are 
converted  into  food  for  man  and  beast,  and  thus  places 
us  on  the  highway  of  sure  and  rapid  improvement. 

These  practical  results,  which  are  the  "basis  of  that 
material  prosperity  in  which  taste,  and  literature,  and 
the  graces  of  life  find  their  natural  growth,  are  "by  no 
means  to  be  disregarded.  But  this  is  not  all.  The 
study  of  chemical  science  reveals  to  the  mind  a  beauty 
and  harmony  in  the  material  world,  to  which  the  unin- 
structed  eye  is  blind.  It  shows  us  all  of  the  kingdoms 
of  nature  contributing  to  the  growth  of  the  tiniest  plant, 
and  feeding  the  germ,  as  it  were,  by  the  inter-revolution 
of  their  separate  spheres.  It  shows  us  how  through 
fire;  or  analogous  decay,  all  forms  of  life  are  returned 
again  to  the  kingdoms  of  nature,  from  which  they  were 
derived.  Without  encroaching  upon  the  domains  of 
the  astronomer,  it  reveals  to  us  still  more  wonderful 
relations  of  distant  orbs,  which  affect  not  only  the  out- 
ward sense,  but  supply  the  very  forces  which  we  em- 
ploy in  our  contest  with  the  powers  of  nature.  It  un- 
veils to  us  a  thousand  mysteries  of  cloud  and  rain,  of 
frost  and  dew,  of  growth  and  decay,  and  unfolds  the 
operation  of  those  silent  yet  irresistible  forces  which 
are  the  life  of  the  world  we  inhabit. 

But  the  study  of  nature  is  worthy  of  being  pursued 
with  a  still  nobler  aim.  The  glory  of  the  Deity  shines 
in  every  crystal  and  blooms  in  every  flower.  Every 


8  INTRODUCTION. 

atom  is  instinct  with  a  life  which  the  Creator  has  im- 
parted. The  laws  that  govern  minutest  particles,  as 
well  as  the  grander  revolutions  of  the  heavenly  spheres, 
are  but  the  expression  of  His  will.  The  reverent  study 
of  nature  is  therefore  a  contemplation  of  Deity.  Vague 
and  unsatisfactory  without  the  aid  of  another,  and 
written  revelation,  it  unfolds  to  the  mind  thus  enlight- 
ened, new  and  exalting  evidences  of  the  infinite  wis- 
dom and  beneficence  of  the  Creator  of  the  world. 


1.  THE  Science  of  Chemistry  is  of  the 

rrnstry  tell  us         . 

of  Earth,  Air,    widest  range.     Air,  Earth,  Fire,  and  Water, 
Fire,  and  Wa-   all  belong  to  its  domain. 

It  informs  us  of  the  composition  of  the  rocks  which 
make  up  the  mass  of  the  Earth,  and  of  the  soil 
which  forms  its  surface.  It  tells  us  of  what  Air  is 
made,  and  how  it  supplies  the  wants  of  animal  and 
vegetable  life.  It  separates  Water  into  gases,  and  re- 
produces it  again  by  uniting  them.  It  informs  us  of 
the  nature  of  Fire,  and  of  the  changes  which  take 
place  in  combustion. 

2.  It  tells  us  of  what  plants  are  formed, 

What  of  met- 

als,piants,and  and  what  becomes  of  them  when  they 
decay  and  disappear.  It  tells  us  how  to 
produce  metals  from  ores,  wines  from  fruit,  liquors 
from  grain,  and  shows  us  the  changes  which  take  place 
in  the  formation  of  all  these  substances.  Almost  all 
transformations  which  occur  in  the  materials  around 
us,  as,  for  example,  of  iron  into  rust,  of  wood  or  coal 
into  gas,  of  food  into  flesh,  it  belongs  to  Chemistry  to 
describe  and  explain. 

3.  As  all  of  these  changes  result  from 

Wliy   does    it  *'«'"•  •  ,          /. 

treat    of  at-    the  action  oi  the  minute  particles  01  mat- 
ter on  each  other,  it  is  necessary  first  to 

consider  the  subject  of  Atoms. 

1* 


10  INTRODUCTION. 

Why  of  Heat       4.  As  the  most  of  them  depend  on  changes 

and  light?  _  .        . 

of  temperature,  it  is  necessary  in  the  first 
part  of  the  work  to  consider  the  laws  and  effects  of 
Heat.  As  these  laws  are  best  understood  from  their 
analogy  to  the  laws  of  Light,  and  as  Light  has  an  import- 
ant influence  in  many  chemical  processes,  a  brief  chapter 
on  Light  precedes  the  chapter  on  Heat  and  its  various 
effects. 

5.   As  many,  and  perhaps  all  chemical 

Why  is  Elec-       .  .    t     , 

tricity  intro-  changes,  are  accompanied  by  electrical 
duced?  phenomena,  it  is  also  important  to  dwell 

briefly  on  the  subject  of  Electricity  before  proceeding 
to  what  is  more  strictly  the  science  of  Chemistry. 
The  first  part  of  this  work  is,  therefore,  devoted  to  the 
consideration  of  these  subjects ;  or,  in  other  words,  to 
the  Science  of  Physics. 


I.-FHYSICS. 


CHAPTER  I, 

ATOMS  AND  ATTRACTION. 

Of  what  is  1*  ATOMS.  —  All  matter  is  supposed  to  be 

matter  compo-    composed  of  exceedingly  minute  spherical 

sed?      What  ,  • 

is  said  of  or  spheroidal  particles,  which  are  held  to- 
gether by  their  mutual  attraction,  and  are 
never  themselves  subdivided.  These  particles  are  com- 
monly called  atoms.  There  is  reason  to  believe  that 
the  atoms  of  different  substances  differ  from  each  other 
in  weight  and  perhaps  in  size.  The  belief  that  they 
are  never  subdivided  is  not  based  on  their  extreme 
minuteness,  but  on  other  grounds,  to  be  mentioned 
hereafter. 

2.  MINUTENESS   OF   ATOMS.  —  Their  mi- 

How  is  the  mi- 

nutcnessofat-    nuteness  is  shown  by  the  fact  that  a  sin- 

oms  shown?         glg    gmin    Qf  mugk   wm    fiu    ft    rOQm   with 

its  fragrant  particles  for  years,  without  suffering  any 
considerable  loss  of  weight.  The  number  of  atoms  it 
gives  off  during  that  time  is  beyond  computation. 

4.   ELEMENTS.  —  There  are  at  least  sixty 

Define  and  il-  W  ;"  , 

lustrate  an  ele-    different  kinds  of  matter.   Each  kind  which 

cannot  be  separated  into  other  kinds  is  called 

an  elementary  substance,  or  simply  an  element.     Iron 


12  ATOMS. 

and  carbon  or  charcoal  are  elements.  Iron  rust,  on  the 
other  hand,  is  a  compound.  There  are,  of  course,  as 
many  different  kinds  of  atoms  as  there  are  of  elements. 

5.  COHESION. — The  force    which  binds 

What  is  Coke-  r     .  ,  .     -.   .         i,    j 

sion?  lllus-  together  atoms  of  the  same  kind  is  called 
trate  the  sub-  fae  attraction  of  cohesion,  or  simply  co- 
hesion. In  the  more  tenacious  substances? 
such  as  iron  or  copper,  the  force  of  cohesion  is  im- 
mense. The  strength  of  a  horse  is  insufficient,  for  ex- 
ample, to  break  an  iron  wire  one-fourth  of  an  inch  in 
thickness.  It  is  because  in  every  section  of  the  wire 
the  atoms  attract  each  other  with  a  superior  force.  And, 
as  we  may  easily  imagine  a  thousand  sections  in  every 
inch  of  the  wire,  we  may  see  that  there  is  in  every  inch 
a  force  of  attraction  constantly  exerted  superior  to  the 
strength  of  a  thousand  horses.  Attraction  between  un- 
like atoms  in  contact  with  each  other,  as  between  glue 
and  the  wood  to  which  it  is  applied,  is  called  adhesion. 

6.  GRAVITATION. — Unlike   the   force  of 
Station™™'    attraction  mentioned  in  the  preceding  para- 
graph, gravitation  acts  at  all  distances.     It 

is  the  reason  of  the  weight  of  bodies,  one  body  weigh- 
ing twice  or  three  times  as  much  as  another,  because  it 
has  twice  or  three  times  the  quantity  of  matter  to  at- 
tract and  be  attracted  by  the  earth. 

7.  CHEMICAL  ATTRACTION  OR    AFFINITY. 

What  ^s  Che- 

mical  Attrac-  The  force  which  unites  unlike  atoms  into 
twn  or  Affim-  compOUn(is  possessing  new  properties  is 
called  chemical  attraction  or  affinity. 
Thus  iron  and  oxygen  unite  by  chemical  attraction  to 
form  iron  rust,  a  substance  different  from  either.  So 


ATOMS.  13 

the  gas  chlorine  ana  the  metal  sodium  unite,  as  will  be 
hereafter  seen,  to  form  common  salt.  When  substances 
become  thus  united  by  chemical  affinity,  the  resulting 
compound  is  not  a  mere  mixture,  with  properties  of 
both  constituents,  as  when  salt  and  sugar  are  mixed  ; 
it  is,  on  the  contrary,  a  new  substance  with  properties 
of  its  own. 

8.  DISTANCE  OF  ATTRACTION. — The  forces 

Do  the  forces        ,  ,  ,        .  .,     t 

of  Cohesion  P*  attraction  above  mentioned,  with  the  ex- 
and  Chemical  ception  of  gravitation,  act  only  at  immeasu- 

Affimty  act  at  J 

great  dlstan-  rably  small  distances.  Two  plates  of  glass 
an  inch  apart  do  not  attract  each  other  ;  even 
when  brought  close  together  they  will  not  remain  at- 
tached. But  if  powerfully  pressed,  the  atoms  are  brought 
within  the  range  of  the  force  of  cohesion,  and  cannot 
again  be  separated.  So  iron  and  oxygen  will  not  at- 
tract each  other  from  a  distance,  but  when  brought  to- 
gether, unite  in  consequence  of  their  chemical  attraction. 

9.  ILLUSTRATION. — The  action  of  the  three 

Illustrate    the     . 

three  different    is  illustrated  in  a  falling  drop  of  water.    Al- 

ktractSionf  "^  ^n^y  nolds  togetner  tne  atoms  of  oxygen 
and  hydrogen  which  make  up  each  particle 
of  water.  Cohesion  unites  the  particles  of  water  thus 
formed,  to  make  the  drop,  and  gravitation  causes  the 
coherent  drop  to  fall. 

10.   THREE  STATES  OF  MATTER. — There 

What  are  the  f 

three  states  of  are  three  distinct  states  or  conditions  01 
matter?  matter — the  solid,  the  liquid,  and  the  gas- 

eous, and  almost  all  substances  may  be  made  to  assume 
each  of  these  states.  Thus,  a  piece  of  solid  sulphur, 
if  heated  up  to  a  eertain  point,  melts  and  becomes 


14  ATOMS. 

liquid.     If  the  liquid  sulphur  be  exposed  to  a  still  higher 

temperature,  it  passes  off  in  the  form  of  a  vapor  or  gas. 

11.   CONTACT    OF    ATOMS.  —  The    atoms 

Are  atoms  in    of  matter  are  not  supposed  to  be  in  ab- 

contact  ? 

What  is  the   solute    contact    in    either   solids,    liquids, 


of    or  gaseS"       This    is    lnferred    fr°m  the  fact 

cohesion  in  bo-  that  all  substances  may  be  diminished  in 
bulk  by  pressure.  But  in  solid  bodies  the 
attraction  of  cohesion  between  the  atoms  is  strongest, 
and  they  are  more  nearly  and  firmly  bound  together. 
In  liquids,  cohesion  is  less  than  in  solids,  and  the  atoms 
are  farther  separated.  In  gases,  cohesion  is  entirely 
overcome,  and  but  for  gravity,  the  atoms  would  sepa- 
rate themselves  indefinitely. 

Heat  is  the  main  cause  of  this  difference  in  cohesion. 
This  subject  will  be  more  fully  considered  in  the  chap- 
ter on  Heat  or  Caloric.* 

*  The  subject  of  crystalization  belongs  to  Physics,  and  in  a  strictly 
scientific  arrangement,  would  be  considered  at  this  point.  The  student 
will  find  the  most  accessible  illustrations  of  the  subject  in  the  Salts, 
which  are  considered  later  in  the  work,  and  it  has  therefore  been  in- 
troduced in  the  chapter  which  treats  of  these  compounds.  It  is  to  be 
borne  in  mind  that  what  is  there  stated,  relates  to  other  compounds 
and  to  elementary  substances,  as  well  as  to  salts. 


LIGHT.  15 


CHAPTER  II. 

LIGHT. 
12.    CHEMICAL  ACTION  OF  LIGHT. — Da- 

Jn  what   cases 

does  light  act    guerreotype  pictures  are  produced  by  the 

chemically?        chemical    action    of    light<       So    Hght    actg 

chemically  in  converting  water  and  irhe  carbonic  acid 
of  the  air  into  vegetable  matter.  The  action  of  light 
in  these  cases  will  be  explained  hereafter.  The  present 
chapter  is  devoted  to  the  consideration  of  its  nature  and 
more  important  laws. 

13.  LIGHT  is  WITHOUT  WEIGHT. — While 

wefht?  Uffki  the  effects  of  tight*  and  the  laws  according 
to  which  they  take  place  are  well  under- 
stood, philosophers  differ  with  respect  to  its  nature.  It 
is,  however,  agreed  that  light  is  imponderable,  or  without 
weight,  this  being  inferred  from  the  fact  that  an  illu- 
mined object  weighs  no  more  than  the  same  object 
when  unillumined. 

14.  NEWTON'S  THEORY. — Newton  main- 

What  is  New-         .  .          /i    •  i      i  • 

ton's  theory  ?      tamed  that  light  is  a  fluid  thinner  or  more 

Nation  of sTglt     Sllbtle  than   ^  OT  **?    ^    but  Composed 

produced?-  like  these  of  minute  particles,  constantly 
given  off  from  the  sun  and  all  luminous  objects.  He 
supposed  that  it  is  this  substance  passing  into  the  eye 
that  produces  the  sensation  of  sight,  as  the  fine  particles 
of  fragrant  matter,  passing  off  from  flowers,  produces 
the  sensation  of  smell. 


16  LIGHT. 

15.    THEORY    OF    VIBRATION. — Another 
What  is  the   view  is  that  the  fluid  above  described  does 

other    view   of 

the  nature  of  not  pass  from  the  sun  and  other  luminous 
objects  to  the  eye,  but  fills  the  space  be- 
tween them  and  serves  as  a  medium  for  producing  the 
sensation  of  light,  as  the  air  does  for  producing  sound. 
TJ,  .  .,.  16.  When  a  bell  is  struck  its  vibrations 

Illustrate  this 

view  ?  are  communicated  to  the  air,  and  so  to  the 

ear,  producing  the  effect  of  sound.  So,  according  to  the 
view  of  light  last  mentioned,  vibrations  are  caused  by 
some  means  in  the  sun  and  certain  other  bodies,  which 
being  rapidly  transmitted  through  the  fluid  above  men- 
tioned, produce,  when  they  fall  on  the  eye,  the  sensa- 
tion of  light. 

17.  EXISTENCE  OF  THE  SUPPOSED  FLUID. 

How     is    this 

fluid  known  to  Such  a  fluid  as  this  theory  requires  is  known 
to  exist  in  the  spaces  between  the  heav- 
enly bodies,  by  the  influence  which  it  exerts  on  their 
motions,  and  is  supposed  to  pervade  all  substances,  whe- 
ther solid,  liquid  or  gaseous,  occupying  the  spaces  be- 
tween their  pores.  It  is  called  ether,  but  has  no  rela- 
tion to  the  chemical  and  medicinal  liquid  of  the  same 
name. 

18.  BOTH  VIEWS  EXPLAIN  THE  FACTS. — 
ther  view  ex-    For  tne  explanation  of  most  of  the  facts 

^rac~  and  laws  of  light  it;  matters  little  which 
view  is  taken.  Thus,  it  is  certainly  true 
that  light  is  reflected  from  mirrors,  whether  we  suppose 
it  a  subtle  fluid,  and  that  its  reflection  is  the  glancing 
off  of  its  particles  from  the  polished  surface,  as  a  ball 
thrown  obliquely  against  the  side  of  a  house  glances 


/  OF   THE  \ 

f  UNIVERSITY   ) 

LIGHT.  17 

off  from  it,  or  whether  we  suppose  it  to  consist  of  vi- 
brations, which  are  made  to  glance  off  as  the  vibrations 
of  the  air  in  the  case  of  echoes. 

19.  The  first,  or  Newtonian  theory,  ena- 
advantagl  of  ^es  us  to  explain  the  leading  facts  more 
the  Newtonian  simply  and  clearly,  and  is  therefore  em- 

theory  ?  .          . 

ployed  in  this  work  for  this  purpose.  The 
definitions  and  laws  of  light  are  stated  in  the  language 
of  that  theory. 

What  is  a  ray  20.    RAY    AND    MEDIUM  DEFINED. A    ray 

°lustrate  ?    the     °^  ^§nt  *S  a  ^me  °^  Partic^S  of  light.       In 

subject.  such  rays  or  lines  of  particles,  light  is  con- 

stantly passing  off  from  all  visible  objects.  From  every 
part  of  the  book  before  the  student,  for  example,  it 
passes  into  the  eye,  enabling  him  to  know  the  nature 
of  the  object.  If  the  book  be  taken  into  a  dark  room 
it  is  no  longer  visible,  because  it  obtains  no  light  which 
it  may  afterward  reflect  to  the  eye. 
W1  ,  .  A  medium  is  any  space  or  substance 

w  liat  is  a  me- 
dium? through  which  light  passes. 

n.     .-,    ,  21.  LAWS    OF   LIGHT. — The   more   im- 

Give  the  laws 

of  light  ?  portant  laws  of  the  radiation  of  light  are 
the  following  : 

1.  Rays  of  light  proceed  from  ev- 
ery point  of  luminous  objects  in  every 
direction.     They  proceed,  for  exam- 
ple, from  every  point  of  the  sun's  sur- 
face. 

2.  They  proceed  in  straight  lines.    Light,  for  example, 
comes  to  us  in  straight  lines  from  the  sun. 

3.  They  diverge  as  they  proceed.     This  is  illustrated 


18  LIGHT. 

in  the  figure,  the  central  point  being  supposed  to  be 
a  star  or  other  source  of  light. 

22.   DIVERGENCE  OF 
Explain      the 

divergence     of    LIGHT. By  the   diver- 

rays  of  light.      gence  of  rayg    Qf  Hght 

is  meant  that  they  spread  them- 
selves over  more  space,  the  further  they  proceed  from 
their  source.  This  is  illustrated  in  the  figure,  where 
the  light  of  a  candle  is  represented  as  passing  through 
a  window,  and  illumining  a  larger  space  on  the  opposite 
wall. 

23.  LAW  or  DIVERGENCE. — When  the  dis- 

Give  the  law  of  . 

divergence,and  tance  is  doubled,  the  surface  that  light 
illustrations.  win  coyer  ig  quadrUpled.  This  is  also 

illustrated  in  the  figure.  The  wall  being  twice  as  far 
from  the  candle  as  the  window,  the  light  covers  four 
times  the  surface.  If  the  distance  of  the  wall  were 
three  times  that  of  the  window,  the  surface  covered 
would  be  nine  times  as  large  as  the  window ;  if  four 
times,  the  surface  covered  would  be  sixteen  times  as 
large.  It  is  evident  from  these  figures  that  the  surfaces 
covered,  increase  as  the  squares  of  the  distances.  The 
light,  of  course,  diminishes  in  intensity  in  the  same 
proportion,  as  it  is  thus  spread  over  greater  surface.  At 
four  times  the  distance,  it  has  only  one-sixteenth  the 
intensity,  and  so  on. 

24.  REFLECTION  OF  LIGHT. — If  a  ball  of 

Explain      the     . 

reflection     of   ivory  or  other  material  be  thrown  perpen- 
dicularly against  any  hard  plane  surface,  it 
will  return  in  the  same  line ;  if  it  be  thrown  obliquely, 


LIGHT.  19 

it  will  glance  off  with  the  same  degree  of  ob- 
liqueness in  the  other  direction.  Light  is  re- 
flected from  plane  surfaces  in  the  same  manner. 
This  reflection  is  illustrated  in  the  figure, 
which  represents  a  mirror,  and  a  ray  of  light 
falling  upon  it  and  again  re-fleeted. 

25.  APPARENT  PLACE  CHANGED  BY  RE- 
Explam    the    FLECTION.  —  As  we  always  seem  to  see  an 

change  of  ap- 

parent   place    object   in  the  direction  from  which  its  rays 

by  reflection.  .  ,  .   .        . 

enter  the  eye,  a  mirror  which  changes  the 
direction  of  the  rays  will  change  the  apparent  place 
of  the  object.  Thus,  if  the  rays  of  the  sun  fall  oblique- 
ly upon  a  mirror,  and  are  reflected  to  the  eye,  we  shall 
seem  to  see  the  sun  in  the  mirror,  in  the  direction 
which  the  rays  have  acquired  after  reflection. 

26.  CONCAVE   MIRRORS.  — 
Tf  tirZl   On  considering  that  rays  are 
converge  rays    reflected  from  plane  surfaces 

with  the  same  degree  of  ob- 


liquity with  which  they  fall  upon  them, 

we  shall  be  able  to  comprehend  how  it  is 

that  concave  mirrors  have  the  property  of  converging 

rays  of  light,  or  bringing  them  together  in  a  point. 

A  number  of  small  plane  mirrors,  situated  obliquely 
toward  each  other,  as  represented  in  the  figure,  and  as 
they  might  be  arranged  in  a  bowl  or  saucer,  would 
evidently  have  this  effect.  As  a  concave  mirror  may 
be  regarded  as  made  up  of  innumerable  plane  mirrors, 
similarly  arranged,  it  would  obviously  be  productive  of 
the  same  effect. 


20  LIGHT. 

27.    REFRACTION. — Re- 

fc£ion?Re~    fraction  is  the   change  of 
direction  which  a  ray  expe- 
riences in  passing  obliquely  from  a  rarer 
into  a  denser  medium,  or  the  reverse. 

28.  The  figure  represents  a  block  of  glass, 
£r^am    the    ftnd  shows  tne  direction  which  a  ray -of 

light  would  take  on  entering  and  emerging 
from  it.  On  entering,  it  makes  a  bend,  and  passes  on 
through  the  glass  less  obliquely  ;  that  is,  more  nearly  in 
the  direction  of  a  line  drawn  perpendicularly  to  the  sur- 
face of  the  glass,  and  continued  through  it.  On  passing 
out  again  it  would  be  bent  away  from  such  an  imagina- 
ry perpendicular  line,  and  re-assume  its  previous  course. 

29.  ANOTHER  STATEMENT  OF  THE  LAW.- — 

Give    another 

statement  of  As  the  perpendicular  has  only  an  imagina- 
YY  existence?  ^  ig  perhaps  easier  to  fix  in 
the  mind  the  changes  of  direction  of  rays 
passing  in  and  out  at  regular  surfaces  thus :  A  ray,  on 
entering  a  denser  medium  pursues  within  it  a  course  fur- 
ther from  the  nearest  portion  of  the  surface  than  its  origi- 
nal course  would  be  if  continued.  And  a  ray  entering  a 
rarer  medium  takes  a  course  nearer  the  nearest  portion  of 
the  surface  than  its  original  course  would  be  if  continued. 
These  statements  are  true  for  all  plane  or  uniformly 
curved  surfaces. 

30.  ILLUSTRATION. — A 
Illustrate  by  a    com  placed  m  ft  tea_cnpj  ag 

represented  in  the  figure, 
so  as  to  be  barely  concealed  from  the 
eye,  will  be  rendered  visible  by  filling  the  cup  with  water. 


LIGHT.  21 

The  surface  of  the  water  furnishes  a  point  of  transi- 
tion from  a  denser  to  a  rarer  medium,  and  the  direction 
of  the  ray  is  thereby  changed  in  accordance  with  the 
law  above  stated.  It  is  thereby  enabled  to  turn  a  cor- 
ner, as  it  were,  and  come  to  the  eye. 

31.    TRIANGULAR    PRISM.  —  Bearing    the 

What      effect  ^ 

has  a  prism  on   rules  last  given  in  mind,  it  will  be  readily 

arayof  light? 


ing  through  a  prism  must  be  such  as  is 
represented  in  the  figure.  The  ray  may 
be  supposed  to  start  from  below  or  above 
the  prism.  The  line  of  its  passage  through 
the  glass  will  be  the  same  in  either  case. 

32.  Let  us  suppose   it  to  pass  upward 

Mustrate    the    from  a  bit  Qf  white  paper  Qr  other  object  to 

the  eye  of  an  observer  above.  The  appa- 
rent place  of  the  object  will  be  changed.  It  will  be  seen 
still  beneath  the  prism,  not  where  it  actually  is,  but  in 
the  direction  in  which  the  ray  points  as  it  enters  the 
eye.  This  experiment  may  be  made  equally  well 
with  the  water  prism  described  in  the  next  paragraph. 

33.  CONSTRUCTION  or  A  PRISM. 

How    may     a 

prism  be  con-  The  prism  commonly  used  in 
optical  experiments  is  of  solid 
glass.  In  lack  of  this,  its  place  may  be  rea- 
dily supplied  by  the  water  prism  represented  in  the  fig- 
ure. A  strip  of  window  glass  is  to  be  scratched  with  a 
file  and  broken  into  three  pieces  of  equal  length.  These 
are  set  up,  as  represented  in  the  figure  upon  another  bit 
of  glass  previously  warmed,  and  thickly  covered  with 
sealing  wax.  When  the  wax  is  cooled,  and  the  bits 


22  LIGHT. 

of  glass  which  it  holds  will  stand  alone,  the  corners 
where  they  meet  are  also  closed  with  sealing  wax. 
The  prism  is  then  filled  with  water,  taking  care  not  to 
moisten  the  upper  edges,  and  a  glass  top  is  afterward 
attached  by  wax. 

34.     ACTION   OF  THE 
Explain    the   LENS   —  The     property 

action  of   the  A 

convex  lens.         which  a  COI1V6X  lens  pOS- 

sesses  of  converging  rays 
of  light  and  heat,  and  bringing  them 
together  in  a  point,  is  also  a  consequence  of  refraction. 
All  of  the  rays  which  fall  upon  its  surface  are  bent,  as 
shown  in  the  case  of  the  prism  ;  but,  owing  to  its  shape, 
they  are  bent  in  diiferent  degrees  and  directions,  so  that 
they  all  meet  in  a  point.  This  point  is  intensely 
bright  if  brought  on  a  dark  object,  and  is  called  the 
focus. 

35.  There  is  another  law  of  refraction 

Explain   ano-  .  •»'•*••»• 

ther  law  of  which  has  not  been  stated,  which  is  essen- 
tial to  a  full  understanding  of  the  convex 
lens.  According  to  this  law,  the  more  obliquely  a  ray 
falls  upon  any  surface  the  more  it  is  refracted  or  bent  out 
of  its  course.  And  it  is  a  consequence  of  the  shape  of  the 
lens,  and  its  greater  steepness  toward  the  edge,  that  of 
all  the  parallel  rays  which  fall  upon  its  surface,  those 
which  fall  furthest  from  the  center  fall  most  obliquely, 
and  enter  the  air  again  more  obliquely.  In  proportion, 
therefore,  as  they  need  to  be  bent  to  be  brought  to  the 
focus,  they  are  thus  bent  by  the  action  of  the  lens. 

36.  ANALYSIS  OF  LIGHT. — It  has,  up  to 
cometed  i-     ^is  point,  been  assumed  that  light  is  sim- 


LIGHT.  23 

pie  in  its  nature,  but  it  may  be  proved  by  experiment 
that  every  beam  of  white  light  such  as  we  receive  from 
the  sun  is  made  up  of  rays  of  different  colors. 

37.  This  maybe  done  by  holding  a  prism 

How      is-   its     . 

composition     in  the  sun  and  al- 
Proved?  lowing  the  light 

to  pass  through  it  and  fall 
upon  an  opposite  wall  or 
screen.  A  beautiful  parti-colored  spot  will  be  produced, 
called  the  solar  spectrum.  The  beam  of  light  which 
enters  the  prism  is  separated  by  it  into  rays  of  seven  dif- 
ferent colors.  The  experiment,  if  performed  in  a  dark 
room,  into  which  light  is  admitted  through  a  very  small 
opening,  is  extremely  beautiful. 

38.  The  rays,  before  entering  the  prism, 

How  does  re-  °      .     r 

fraction  de-  passing  along  together  parallel  with  each 
compose  light?  other?  form  white  H  ht .  but  on  entering 

the  glass  and  emerging  from  it,  each  of  them  is 
refracted  or  bent  out  of  its  course  in  a  different  degree, 
and  they  are  thus  separated,  and  made  to  appear  with 
their  own  colors.  Why  one  ray  is  refracted  more  than 
another  is  not  known.  The  above  experiment  proves 
it  to  be  a  fact,  and  this  is  all  our  knowledge  on  the 
subject. 

Do    lenses  de-  39.      LENSES     DECOMPOSE     WHITE     LIGHT 

compose  light?  AND  RECOMBINE  THE  RAYS. — This  separation 
of  white  light  into  colored  rays  occurs  always  when 
light  passes  through  a  prism ;  but,  for  the  sake  of  sim- 
plicity, this  fact  was  left  out  of  consideration  in  para- 
graph 29,  the  object  in  that  place  being  simply  to 
show  the  general  direction  of  the  light  as  it  passes 


24  LIGHT. 

through  the  prism.  Such  separation  also  occurs  when 
light  passes  through  a  lens,  but  the  different  colored 
rays  on  emerging  again  from  different  points  of  the 
lens  overlap  each  other,  and  are  in  great  part  united 
again  to  form  white  light. 


NATURE    OF    HEAT.  25 


CHAPTER  III. 

HEAT. 

Section  1. — Nature  and  Sources  of  Heat. 
Has    heat        4Q.  NATURE  OF  HEAT. — It  was  remarked 

weiqht?    Give     .  , 

an  Illustration  in  the  commencement  01  the  chapter  on 
light,  that  philosophers,  although  acquainted  with  its 
facts  and  laws,  differed  in  opinion  as  to  its  nature.  The 
same  is  true  of  heat.  It  is  agreed,  however,  that  heat, 
like  light,  is  imponderable,  or  without  appreciable 
weight ;  this  being  known  from  the  fact  that  a  heated 
body  weighs  no  more  than  a  cold  one. 

41.  If  the  end  of  a  bar  of  iron  is  heated,  the 
other  end  soon  becomes  hot.  There  is  no  doubt 
as  to  the  effect,  and  it  would  seem  that  something 
must  have  passed  from  the  fire,  along  through  the 
rod  to  produce  it.  But  we  do  not  certainly  know 
that  any  substance  has  been  thus  transmitted.  It  may 
be  that  heat  is  analogous  to  sound,  and  produced  by 
vibrations.  Being  thus  in  doubt,  we  say  that  the  na- 
ture of  heat  is  not  understood. 

42.  MECHANICAL   THEORY. — One  view  is 

State    the  me-  .  •          r-  ^ 

chemical  theo-  that  a  very  subtle  fluid  coming  from  the 
ry'  fire  has  actually  passed  along  through  the 

mass  of  metal,  and  from  that  into  the  hand,  and  so 
caused  the  sensation  of  warmth  or  heat.  And  this 
supposed  substance  is  called  heat,  or  caloric. 

2 


26  HEAT. 

What  is  the  43.  THEORY  OF  VIBRATION.  —  Another 
bration?  view,  corresponding  to  the  second  view  ol 
light,  is,  that  heat  is  not  a  fluid,  but,  like  light,  the  result 
of  vibration  in  the  ether  which  is  every  where  present. 
The  vibrations  which  produce  the  sensation  of  heat 
are,  of  course,  different  from  those  which  produce  that 
of  light,  as  the  movements  of  the  air  which  produce 
heavy  and  sharp  sounds  are  different.  We  must  sup- 
pose, indeed,  in  the  former  case,  that  a  much  greater 
difference  exists.  But  it  is  assumed  that  both  are  the 
result  of  vibrations  of  some  kind. 

44.  ILLUSTRATION.  —  When  a  bell  is  struck 
Give  the  illus-    ^s  vibrations  are  communicated  to  the  air, 

tration. 

and  so  to  the  ear,  producing  the  effect  of 
sound.  So,  according  to  this  view,  vibrations  of  a  pe- 
culiar kind  are  caused  by  some  means  in  the  sun,  and 
all  sources  of  heat,  and,  being  rapidly  transmitted 
through  the  ether,  produce,  when  they  fall  upon  our 
bodies,  the  sensation  of  heat.  So  the  bar  heated  at 
one  end  becomes  hot  at  the  other,  because  certain  vi- 
brations, originated  in  the  fire,  are  gradually  transmit- 
ted through  the  ether,  and  the  iron  which  it  pervades, 
to  the  other  end. 

45.  THE  FACTS  ARE  DEFINITELY  KNOWN. 

What    is    the 

limit  of  our    It  may  seem  strange    to  the    reader  that 


Cct?°  there  should  be  this  doubt  in  relation  to  so 
common  a  subject  as  heat.  But  there  is  a 
similar  limit  to  our  knowledge  in  most  of  the  sciences. 
In  physiology,  for  example,  we  know  that  muscle,  and 
bone,  and  other  parts  of  the  body,  are  produced  from 
the  blood,  and  that  life,  or  vital  force,  is  essential  to 


SOURCES    OF    HEAT.  27 

their  production  ;  but  how  the  vital  force  operates  we 
do  not  know.  But,  as  in  physiology  this  ignorance 
does  not  prevent  us  from  comprehending  the  structure 
of  the  human  body  and  the  uses  of  its  different  organs, 
so  ignorance  in  relation  to  the  nature  of  heat  does  not 
interfere  with  the  acquisition  of  the  most  perfect  knowl- 
edge of  its  effects,  and  the  laws  according  to  which 
they  happen. 

46.     THE    MECHANICAL    THEORY    HERE 

What    theory  T      ,,  ,        ~ 

is  adopted  in    ADOPTED.  —  In  the  present  volume  the  for- 


mer  Of  the  views  which  have  been  men- 

Explain  it. 

tioned  is  adopted,  and  heat,  like  light,  is 
assumed  to  be  an  exceedingly  subtle  imponderable  fluid. 
And,  to  return  to  the  example  of  the  heated  bar,  it  grows 
hot  at  the  end  farthest  from  the  fire  because  the  fluid 
actually  passes  through  its  solid  substance,  and  is  so 
communicated  to  the  hand. 

47.     DEFINITION   OF    COLD.  —  Cold    is   a 

what  is  meant 

by   the    term    relative  term  signifying  the    comparative 
absence  of  heat.     But  the   coldest  bodies 
which  we  know  of,  as  ice,  for  example,  contain  heat, 
and  may  be  made  colder  by  its  withdrawal. 

48.  SOURCES  OF  HEAT.  —  The  principal 

State  the  prin- 

cipal  sources  sources  or  heat  are  the  sun  and  fixed  stars, 
of  hmt.  chemical  action,  electricity,  and  friction. 

It  is  by  no  means  certain  that  these  should  be  distin- 
guished as  different  sources  ;  for  the  heat  of  the  sun 
may  be  due  to  chemical  action,  and  electricity  is,  as 
we  know,  excited  both  by  chemical  action,  and  by 
friction. 


28  HEAT. 

Hmmuchheat  49.    Q.UANTITY  OF    HEAT    THE    SUN    SENDS 

does    the.    sun  , 

send  to  the  TO  THE  EARTH. — The  sun  sends  enough 
earth?  jieat  to  tne  eartn  every  year  to  melt  a  shell 

of  ice  enveloping  the  earth  a  hundred  feet  thick.  This 
may  be  ascertained  by  observing  what  thickness  the 
average  heat  of  the  sun  will  melt  per  minute,  and  then 
calculating  the  quantity  for  a  year.  The  method  ac- 
tually pursued  is  slightly  different  from  this,  but  the 
same  in  principle.  The  sun,  in  fact,  sends  a  larger 
amount  of  heat  to  the  earth  than  is  above  stated,  but 
40  per  cent,  of  it  is  absorbed  by  the  atmosphere.  The 
quantity  above  given  is  the  remaining  60  per  cent. 

50.   TOTAL  QUANTITY  OF  HEAT  THE  SUN 

Howmuchheat  . 

is  given  out  by     GIVES    OUT. KllOWlllg    flOW    much    COniCS 

the  sun  audits    t     th          th      d  it    atmosphere,  it  is  easy 

atmosphere  ?  * 

to  calculate  how  much  starts  from  the  sun. 
It  is  just  in  proportion  to  the  extent  of  the  whole  visi- 
ble heavens,  as  seen  from  the  sun,  compared  to  the  space 
occupied  by  the  earth,  as  seen  from  the  same  point. 
By  making  the  calculation  it  is  ascertained  that  a 
quantity  of  heat  is  given  out  from  the  sun  in  a  year 
which,  if  it  all  came  to  the  earth,  would  melt  a  crust 
of  ice  nearly  4000  miles  thick,  or  a  quantity  which 
would  melt  every  minute  a  crust  nearly  thirty-seven 
feet  in  thickness.  But  the  heat  of  a  blast-furnace, 
if  kept  up  constantly  to  the  highest  point,  would  melt 
'but  a  little  over  the  thickness  of  five  feet  of  ice  per  min- 
ute. The  sun's  surface  is,  therefore,  more  than  seven 
times  as  hot  as  the  glowing  surface  of  the  fire  of  a 
blast-furnace. 


SOURCES     OF     HEAT.  29 

What  is  said  51.    HEAT    OF    THE    FIXED     STARS. The 

of  the  heat  of 

fixed  stars?  fixed  stars  are  suns  of  other  systems,  and 
sources  of  heat,  like  our  own  sun.  And  their  number 
is  so  great,  that  notwithstanding  their  distance,  they 
exert  a  very  important  eifect  on  the  temperature  of 
the  earth.  It  is  estimated  that  they  give  us  nearly  as 
much  heat  as  the  sun,  and  that  without  this  addition  to 
the  sun's  heat,  neither  animal  nor  vegetable  life  could 
exist  upon  the  earth. 

52.     HEAT    OF    CHEMICAL    ACTION    AND 

Give  examples 

of  heat  pro-    ELECTRICITY. — We  shall  see  hereafter  that 

mic'al   ^action     heat  ls  evolved    in  almost  al*  Cases    of  che- 

and  by  elcc.tri-    mical  action.     Indeed,  the  heat  of  our  fires 
has  this  origin,  as  will  be  explained  in  an- 
other  chapter.     The    heat    of  the    lightning  is  devel- 
oped by  electricity. 

Give  examples  53.     HEAT     FROM    FRICTION. The    heat 

°f  jj*j*  P££  produced  by  slight  rubbing  is  sufficient  to 
tion.  set  on  fire  a  phosphorus  match.  Sir 

Humphrey  Davy  produced  heat  by  friction  between 
two  pieces  of  ice.  It  is  said  that  Indians  produce  fire 
by  rubbing  two  sticks  of  wood  together.  Count  Rum- 
ford  caused  water  to  boil  by  boring  a  cannon  beneath  its 
surface.  These  are  all  cases  of  the  production  of  heat 
by  friction. 


30  HEAT. 


Section  2. — Communication  of  Heat. 

54.  Heat  is  communicated  by  conduction,  convection, 
and  radiation.  These  three  modes  of  communication 
will  be  considered  in  the  order  in  which  they  are 
named. 

CONDUCTION. 

Explain    the        55.  Conduction    is  the  passage  of  heat 

%£*uction  f    through  a  body  by  communication  from 

particle    to    particle.      An   iron  wire,  one 

end  of  which  is  held    ' 

o o o o      o o       ^ 

in  aflame,  soon  grows  Q 

hotter  at  the  other,  by  conduction  of  the  heat  of  the 
flame.  The  progress  of  heat  along  a  wire  may  be 
shown  by  fastening  marbles  to  it  with  wax,  as  rep- 
resented in  the  figure,  and  then  heating  one  end  by  a 
lamp.  The  marbles  drop  off  successively,  as  the  heat 
in  its  progress  melts  one  bit  of  wax  after  the  other. 
The  communication  of  heat  from  one  body  to  another 
in  contact  with  it  is  also  a  case  of  conduction. 

56.  WHEN  CONDUCTION  CEASES. — Con- 

When   docs 

conduction  duction  proceeds  toward  the  cooler  por- 
tions of  a  body  until  all  its  particles  be- 
come equally  hot,  just  as  the  absorption  of  water  by  a 
sponge  continues  until  all  its  pores  are  filled.  This 
point  being  reached,  there  is  no  tendency  to  further 
motion  in  the  case  of  the  heat  more  than  in  water. 

57.  THE    METALS  ARE  THE  BEST  CON- 

W hat  substan- 
ces are  the  best    DUCTORS. — -The  earths  and  wood  conduct 

very  slowly;    fine  fibrous  substances,  like 


CONDUCTION.  31 

wool,  cotton,  fur,  and  feathers,  slowest  of  all.  Liquids 
and  gases,  as  will  be  hereafter  seen,  are  non-conduct- 
ors of  heat.  The  superior  conducting  power  of  metals 
is  shown  in  the  rapidity  with  which  an  iron  wire,  one; 
end  of  which  is  held  in  the  flame  of  a  lamp,  grows  hot 
at  the  other  end.  A  splinter  of  wood,  or  a  pipe-stem, 
is  heated  from  end  to  end  much  less  rapidly,  while 
scarcely  any  heat  would  be  communicated  along  a  roll 
of  cotton  cloth,  one  end  of  which  was  inflamed. 

58.  ILLUSTRATION. — The  difference  of 

How  may  the         -    m 

conducting  conducting  power  in  metals  and  earths  may 
al™L°fbeieii-  be  illustrated  by  fastening 
lustrated?  together  by  a  wire,  as  repre- 
sented in  the  figure,  an  iron  nail  and  a 
bit  of  pipe-stem  of  equal  length,  and 
heating  them  over  a  spirit  lamp.  The  end  of  a  match 
having  been  fastened  with  thread  to  each,  it  is  found 
that  the  heat  will  travel  along  the  nail  and  inflame 
the  match  at  its  end  long  before  the  other  match  is  ig- 
nited. 

59.  PROTECTION  FROM  THE  CENTRAL  FIRE 

How    are     we 

protected  from  OF  THE  EARTH. — We  are  protected  from  the 
the  central  heat  centrai  neat  of  the  earth  by  the  non-con- 

of  the  earth  ?  * 

ducting  power  of  the  rocks  and  soil  which 
form  its  outer  crust.  So  a  crust  forms  after  a  time  over 
the  streams  of  lava  which  flow  from  volcanoes  ;  but, 
owing  to  its  non-conducting  power,  the  lava  below  re- 
mains liquid  for  years. 

60.  CONDUCTION  FROM  ONE  BODY  TO  AN- 

Wh  en  does  con-  mi   •  i  •  Ji 

duction  take  °THER- — This  takes  place  most  rapidly 
place  most  ra-  the  more  perfect  the  contact  between  the 

pidly  ? 

two.     Conduction  from  air  or  a  gas  to  a 


32  HEAT. 

solid  is  slow,  because  the  gas  contains  comparatively 
few  atoms,  and  therefore  furnishes  few  points  of  con- 
tact. Between  a  liquid  and  a  solid  it  is  more  rapid,  be- 
cause there  are  more.  A  cannon  ball  would  grow  hot 
much  more  rapidly  in  boiling  water  than  in  air  of  the 
same  temperature.  Between  solid  and  solid,  again,  con- 
duction is  less  rapid,  because  the  surfaces  cannot  so 
adapt  themselves  to  each  other,  like  liquid  and  solid,  so 
as  to  bring  all  their  atoms  together.  This  paragraph 
refers  solely  to  the  passage  of  heat  from  the  atoms  of 
one  surface  into  those  of  the  other.  Th§  further  con- 
duction of  heat  depends  on  the  substance  into  which 
it  has  passed. 

61.  HEATING  WATER.  —  Water  is  sooner 

Why  is  water     .  ..     . 

heated  sooner  heated  m  an  iron  pot,  or  other  metallic 
™ianin°a  vessel,  than  in  one  of  porcelain,  glass,  or 
glass  vessel?  earthen-  ware,  because  the  metal  conducts 
the  heat  through  from  the  fire  more  rapidly.  Cooling, 
or  the  passage  of  heat  outward  when  the  vessel  is  re- 
moved from  the  fire,  goes  on  more  rapidly  in  the  case 
of  the  metallic  vessel  for  the  same  reason.  These 
statements  have  reference  only  to  vessels  which  are  not 
polished.  In  the  case  of  bright  surfaces,  another  prin- 
ciple is  involved  to  be  considered  hereafter. 

62.  CLOTHING.  —  Fibrous  substances,  like 

Exn  am     the  , 

subject  of  do-    wool,  cotton,  and  furs  are  best  adapted  for 


l  clothi«g>  because  they  are  such  poor  con- 
ductors, and  beside,  because  they  contain 
air  shut  in  between  their   fibres,  which   is  a  non-con- 
ductor. as  will  be   hereafter  shown.     The   object  of 
clothing  is  not  to  impart  heat,  but  to  prevent  its  escape 


CONDUCTION. 


33 


from  the  body.  It  -escapes  more  or  less  through  all 
substances,  but  less  rapidly  through  the  fibrous  materi- 
als just  mentioned,  and  therefore  their  superiority  for 
winter  clothing.  If  we  lived  in  an  atmosphere  hotter 
than  our  bodies,  the  object  of  clothing  would  be  to  ex- 
clude heat,  and  the  same  non-conducting  materials  now 
used  would  be  best  adapted  for  this  purpose  also. 
Sometimes  it  is  actually  the  object  of  clothing  to  keep 
out  heat  ;  as,  when  workmen  enter  hot  furnaces  in  cer- 
tain manufacturing  processes.  Thick  clothing,  of  non- 
conducting materials,  is  obviously  best  in  this  case  also. 
In  summer,  coarser  fibre  of  linen,  which  is  a  better 
conductor  than  cotton  or  wool,  is  more  used,  because 
it  conveys  away  the  heat  of  the  body  more  rapidly,  as 
is  desirable  in  the  warmer  season. 

63.     FURS    OF   ANIMALS.  —  We    see,    in 

Why  has    the         ,         .         ,  ,  . 

Deity  varied  what  has  been  stated,  the  reason  why  the 
ninuffl9*  Deity  has  clothed  animals  inhabiting  cold 
climates  with  fine  furs.  While  the  elephant 
of  the  torrid  zone  has  but  a  few  straggling  hairs,  the 
polar  bear  has  a  thick  coat  of  fine  fur  to  keep  in  his  vi- 
tal heat,  and  enable  him  to  endure  the  extreme  rigor 
of  a  northern  climate.  So  the  sea-fowl  has  a  thick 
covering  of  soft  down  to  protect  him  from  the  cold  of 
the  ocean,  while  the  ostrich  has  an  open  coat  of  scanty 
feathers. 
,,r,  ,  •  64.  WARMTH  OF  SNOW.  —  Snow  keeps 

Why  does  snow  r 

tend  to   keep    the  earth  warmer  in  winter  than  it  would 


otherwise  be,  not  because  of  any  heat  it 
imparts,  but  because,  by  reason  of  its  low 
conducting  power,  and   that  of  the  air  which  it  con- 

2* 


34  HEAT. 

tains,  it  prevents  the  escape  of  the  heat  which  is  stored 
in  the  earth  from  the  previous  summer.  But  for  this 
indirect  warming  effect  of  the  snow,  the  cold  of  a  sin- 
gle winter  would  be  sufficient  to  kill  whole  races  of 
plants.  Thus,  the  cold  of  the  winter  weaves  a  garment 
to  protect  the  earth  from  its  own  influence. 
How  do  the  ^'  BUILDING. — In  building,  the  same 
principles  of  principles  apply  as  in  the  case  of  clothing. 
Cpiyinthtcas~e  Bad  conductors,  when  suitable  in  other 
of  buildings?  respects,  are  the  best  materials  for  walls, 
making  a  house  cooler  in  summer  and  warmer  in 
winter.  Wood  and  brick,  for  example,  are  in  this 
respect  better  than  iron.  They  keep  out  the  heat 
in  summer,  and,  though  they  have  the  same  effect 
to  exclude  the  heat  of  the  sun's  rays  in  winter,  they 
more  than  make  up  for  this  by  preventing  the  escape 
of  the  larger  quantity  of  heat  produced  by  the  fires  in- 
side. The  inhabitants  of  the  Arctic  regions  build  their 
winter  huts  of  snow,  and  thus  make  practical  use  of 
its  low  conducting  power.  Double  doors  and  windows 
have  more  than  a  double  effect  in  preventing  the  escape 
of  heat  in  winter,  because  of  the  non-conducting  wall 
of  air  between  them. 
,,„  .  .  ,  66.  REFRIGERATORS. — These  are  double- 

What    is    the 

principle  in-    walled  wooden  box- 


es>  «sed  to 

refrigerators  ?     articles  of  food  from 

the  heat  of  the  summer.  The 
space  between  the  double  walls 
and  top  is  filled  with  pulverized 
charcoal,  which  has  in  itself  very  little  conducting 


CONDUCTION. 


35 


power,  and  again  is  non-conducting  because  of  the  air 
between  the  particles. 

67.  FIRE-PROOF  SAFES. — These  are  constructed  on  the 
same  principle,  the  space  be- 
tween the  double  walls  being 
filled  with  gypsum,  or  some 
other  non-conducting  material. 
They  are  used  as  repositories 
of  valuable  papers  and  other 
property,  for  greater  security  in 
case  of  fire. 

68.  WHY  BODIES  FEEL  COLD  OR  HOT. — 

Why  do  bodies  . 

feel  cold  or  A  metallic  door-knob  feels  colder  than  the 
kot  ?  wood  to  which  it  is  fastened,  although  it 

cannot  actually  be  so.  It  is  because  the  metal  is  the 
best  conductor,  and  carries  off  the  heat  of  the  hand 
more  rapidly.  If  a  piece  of  metal  and  wood  be  placed 
in  a  hot  oven  till  both  become  equally  hot,  as  they  must 
by  long  exposure  to  the  same  heat,  the  metal  will  feel 
hotter  than  the  wood.  It  is  because  the  metal,  by  its 
greater  conducting  power,  supplies  heat  more  rapidly 
to  its  own  surface  to  be  taken  away  by  the  hand. 

69.  SIMPLE  TEST  OF  CONDUCTING  POWER. 

Give  a  simple 

test  for  deter-    Among  bodies  equally  hot,  the   colder  a 

Inducting6  body  feelsjthe  better  conductor  it  is.  That 
power  of  'a  body  this  is  generally  the  case  is  evident  from 
the  last  paragraph.  On  applying  this  test,  we  find  the 
metallic  lamp-stand,  cooler,  and  therefore  a  better  con- 
ductor than  the  table  cover  on  which  it  stands.  In 
an  oven,  or  other  place  where  the  heat  is  greater  than 
that  of  our  bodies,  the  test  would  be  reversed.  For 


36  HEAT. 

the  flow  of  heat  would  be  in  this  case  into  the  hand, 
from  this  highly  heated  object,  and  the  body  that 
brought  it  fastest,  or  felt  hottest,  would  be  thereby 
proved  to  be  the  best  conductor. 

70.  LIQUIDS    NON-CONDUCTORS. — Water 


it    in  a  test-tube  may  be  boiled  at  the  top 
'quids  are  non-    wh jje  jce  frozen  into  the  bottom  will  re- 

conditctors  ?  _ 

main  unmelted.  If  a 
bar  of  metal  with  a  cavity  at  the 
bottom  for  the  ice  were  heated  in 
the  same  way,  the  heat  would  be 
conducted  downward  so  rapidly 
that  the  ice  would  soon  disappear. 

Explain  the         ?!.    FlRE    ON    WATER. — Fire    may  be 
experiment        kindled  on  water  by  pouring  a  little  ether 

with   ether   to  /• 

prove  that  li-    upon  its  surface  and  inflaming 
the  flame  will  be  found 


heat.  t0    have  slight  effect   on  the 

temperature  of  the  water.  And,  what  lit- 
tle effect  it  has,  is  principally  due  to  the 
fact  that  the  glass  or  metal  of  the  containing  vessel 
carries  the  heat  downward  and  distributes  it  to  the 
liquid.  When  water  is  heated  by  a  fire  beneath  it,  it 
is  not  by  conduction,  but  by  another  process,  explained 
in  a  subsequent  paragraph.  The  above  experiment 
may  be  made  in  a  tin  cup  very  nearly  filled  with  water. 
A  tea-spoonful  of  ether  having  been  poured  on  the  water, 
the  bottle  is  to  be  corked  and  set  away,  for  fear  of  ex- 
plosion, from  the  kindling  of  the  ether  which  it  con- 
tains. The  experiment,  as  described,  is  not  in  the 
least  degree  dangerous. 


CONVECTION.  37 

CONVECTION. 

72.  It   has    been   already  shown    that 

Explain    how 

liquids  become  liquids  and  gases  are  non-conductors. 
This  implies  that  they  cannot  be  heated, 
like  a  mass  of  metal  or  other  solid,  by  communi- 
cation of  heat  from  particle  to  particle.  Each  parti- 
cle, on  the  contrary,  receives  its  heat  directly  from  the 
source  of  heat,  and  conveys  it  away,  making  room  for 
others.  Hence  the  term  convection.  In  the  process  of 
boiling  water,  for  example,  the  first  effect  of  the  fire  is 
to  heat  the  lower  layer  of  liquid,  and  thereby  to  expand 
and  make  it  lighter.  It  then  rises  as  a  cork  would  in 
water,  and  gives  place  to  another  portion,  which  be- 
comes heated  and  rises  in.  its  turn.  Thus  a  circula- 
tion is  commenced,  the  warmer  portions  ascending  and 
the  cooler  descending,  which  continues  until  the  water 
boils.  Before  this  happens,  each  particle  will  have 
made  many  circuits,  accumulating  heat  with  each  re- 
turn, but  not  communicating  it  to  others.  Air  and 
gases  become  heated  in  the  same  way. 

73.  CONVECTION   MADE  VISIBLE.  —  The 

How    can   the  .,      ,  , 

circulation  in    circulation   above   described  may  be  ren- 

dered  visible  b  addins  a  little  of  the  "  flow~ 


berenderedvis-     erS  of  Slllphlir"  to  Water  , 
iblc?  .      . 

and  then  heating  it  in 
a  test-tube  over  a  spirit  lamp.  The 
suspended  particles  will  be  found 
to  move  in  the  direction  indicated 
by  the  arrows,  showing  that  the 
water  has  the  same  motion.  The 


38  HEAT. 

upward  current  is  not,  it  is  to  be  remembered,  because 
of  any  tendency  of  heat  to  rise.  Heat,  on  the  con- 
trary, travels  in  one  direction  as  well  as  another. 
But  it  is,  -as  before  explained,  because  hot  water  is 
lighter  than  cold.  Dust  of  bituminous  c.oal  answers 
the  purpose  in  this  experiment  still  better  than  "  flowers 
of  sulphur."  It  is  necessary  to  have  something  that 
will  neither  sink  or  swim,  but  remain  suspended  in 
the  water. 

74.  HEATING  ROOMS. — A  room  becomes 

How    does     a  . 

room  become  heated  by  a  stove  in  the  same  manner. 
heated?  rpne  ^T  ^R  imme(jiate  contact  with  the 

hot  surface  becomes  heated  and  rises.  Cooler  air  comes 
in  from  all  sides  to  take  its  place,  and  be  heated  and 
less  in  turn.  A  circulation  is  thus  established  pre- 
cisely similar  to  that  which  occurs  in  the  flask,  as  rep- 
resented in  the  figure.  Any  light  object,  as  a  feather, 
or  a  flock  of  cotton-wool,  held  over  a  stove  or  an  open 
flame,  will  prove  by  its  ascent  the  existence  of  the  up- 
ward current.  How  rapidly  heat  thus  passes  upward  by 
convection,  may  be  proved  by  holding  the  finger  above 
the  flame  of  a  lamp,  and  then  at  an  equal  distance  at  its 
side,  and  comparing  the  effect. 

How  is  the  at-  ^'    CONVECTION  IN  THE   HEATING  OF  THE 

mosphere heat-  ATMOSPHERE. — Heat  is  distributed  through 
the  earth's  atmosphere  in  the  same  manner. 
At  the  equator,  where  the  surface  is  hottest,  the  air 
heated  by  contact  with  it  rises  and  flows  off  toward  the 
poles,  while  colder  air  from  the  polar  regions  flows  in 
to  take  its  place,  to  be  heated  and  rise  in  turn,  contin- 
uing the  circulation.  But  for  this  arrangement,  the 


RADIATION.  39 

equatorial  regions,  which  are  constantly  receiving  ex- 
cess of  heat  from  the  sun,  would  soon  become  unin- 
habitable by  reason  of  its  accumulation,  and  the  polar 
regions,  from  extreme  cold.  The  currents  or  winds 
thus  produced  are  subject  to  great  irregularities,  which 
are  considered  in  works  on  natural  philosophy. 

RADIATIOK 
76.     The     general    laws    of  radiation 

What  are  the  ° 

laws  of  the  are  the  same  for  heat  as  for  light.  Rays 
™eat?i0n  °f  of  heat  divei'ge  constantly  from  all  points 
of  the  surface  of  all  bodies,  in  straight 
lines  and  in  every  direction  ;  and  the  intensity  of  heat 
varies  inversely  as  the  square  of  the  distance.  The 
latter  point  is  explained  in  the  chapter  on  light. 

77.  HEAT  is  RADIATED  FROM  ALL  BODIES. 

Illustrate    the  .  . 

fact  that  heat  It  is  to  be  observed  that  while  light  pro- 
in  alWradiatl~d  cee(*s  onlv  ^roni  certain  bodies,  heat  pro- 
from  bodies,  ceeds  from  all  points  of  all  bodies  without 
exception.  If  the  mercury  in  a  thermometer  were  fro- 
zen by  extreme  cold,  and  then  hung  in  a  cavity  made 
for  the  purpose  in  a  block  of  ice,  radiation  of  heat  from 
the  ice  would  melt  it,  even  if  there  were  no  air  in  the 
cavity  to  help  melt  it  by  conduction. 

78.  PROPORTION  OF  RADIATION  TO  TEM- 

What   can   be 

said  of  the  pro-    PERATURE. — The  hotter  a  stove  is  the  more 

heat  il  Slves  Ollt'  This  is  obvious,  and  we 
might  naturally  suppose  that  a  stove  twice 
as  hot  as  another  stove,  compared  with  other  objects 
about  it,  would  give  out  heat  just  twice  as  fast.  It 


40  HEAT. 

gives  out  heat,-  in  fact,  more  than  twice  as  fast,  the  ra- 
pidity of  radiation  being  more  than  in  proportion  to  the 
temperature. 

79.   POLISH  is  UNFAVORABLE  TO  RADIA- 

What  are  the  . 

effects  of  rough    TioN.  —  A   coffee-pot    oi    well    brightened 


metal  will  keep  its  contents  hot  much  bet-. 
diation?  ter  than  a  dingy,  blackened  one,  thus  re- 

warding the  housewife  for  her  pains.  The  brightness 
is  not  the  cause  of  this  effect.  It  is  owing  to  the  fact 
that  polished  surfaces  are  more  dense,  and  dense  sur- 
faces do  not  allow  heat  to  pass  readily.  But  if  the  pol- 
ished coffee-pot  be  covered  with  muslin  so  as  to  give  it 
a  less  dense  surface,  radiation  and  consequent  cooling 
will  proceed  more  rapidly  again.  One  would  think 
that  the  polished  surface  beneath  the  cloth  would  have 
the  same  effect  in  retaining  the  heat  as  before,  and  that 
the  cloth  would  still  further  retard  its  escape  ;  but  ex- 
periment proves  that  this  is  not  the  case.  Radiation 
depends  on  the  surface,  without  regard  to  what  is  be- 
neath it,  and  the  superiority  of  the  cloth  as  a  radiator 
is  more  than  sufficient  to  make  up  for  its  non-conduct- 
ing influence.  Rough  uncompact  surfaces,  generally, 
radiate  well.  High  polish  being  unfavorable  to  radia- 
tion, stoves  should  not  be  too  highly  polished.  The 
high  polish  of  soldiers'  helmets  makes  them  much 
cooler  than  if  they  were  made  of  dull  metal. 
,.r,  .  80.  COLOR  DOES  NOT  AFFECT  RADIATION.-^ 

What       effect 

has  color  on    A  black  coat  wastes  no  more  of  the  heat 

of  the  body  by  radiation  than  a  white  one. 

Except  in   the   direct  rays  of  the  sun,  one  is  just  as 

warm  as  the  other.     But  the  former  absorbs  and  imparts 


REFLECTION.  41 

to  the  body  more  of  the  heat  which  comes  to  it  asso- 
ciated with  intense  light,  as  is  the  case  with  the  heat 
of  the  sun,  and  therefore  its  advantage  as  an  article  of 
winter  clothing. 
Tir,  .  .  81.   TRANSMISSION  OF  HEAT. — The  heat 

What  is 

said    of    the    of  the  sun  passes  with  its  light  through 

transmission        ,,  ,  -r»       i  /• 

of  heat  thro'  aU  transparent  substances.  But  heat  from 
bodies  ?  jess  mtense  sources  is  absorbed,  and  in  large 

part  stopped  by  many  substances  which  allow  light  to 
pass :  such  are  water,  and  alum,  and  glass  to  a  less  extent. 
A  glass  plate  held  between  one's  face  and  the  sun  will  not 
protect  it,  but  held  before  the  fire  will  intercept  a  large 
part  of  the  heat.  So  a  glass  lens  or  burning-glass  will 
stop  the  heat  of  a  fire,  instead  of  transmitting  and  con- 
centrating its  raysj  as  it  does  those  of  the  sun.  It  is  a 
singular  fact,  on  the  other  hand,  that  many  substances 
which  allow  heat  to  pass,  effectually  stop  the  light. 
Such  are  black  glass  and  smoked  quartz  crystal.  Rock 
salt  allows  heat  to  pass  so  perfectly  that  it  has  been 
called  the  glass  of  heat. 

82.     REFLECTION    OF    HEAT. — Polished 

What     bodies 

are  the  best  re-    metallic   surfaces  are   the   best   reflectors. 

S53***gJ  Coffee  takes  lonser  to  boil  in  a  brisht  cof- 

subject.  fee-pot,  because  the  heat  is  reflected  from 

the  bright  surface  and  does  not  enter  the  liquid.  If  it 
were  desired  to  heat  a  liquid  as  rapidly  as  possible,  and 
keep  it  hot  as  long  as  possible  in  the  same  vessel,  it 
would  be  wise  to  take  a  dingy  one  for  the  rapid  heat- 
ing of  the  liquid,  and  then  to  polish  it  in  order  to  fasten 
the  heat  in.  Glass  mirrors  do  not  reflect  heat  so  well 
as  those  of  uncovered  metal,  because  of  the  absorbing 


42  HEAT. 

power  of  the  glass,  mentioned  in  the  last  paragraph. 
But  this  absorbing  power  is  very  slight  for  heat  which 
comes  from  an  intense  source  like  the  sun,  so  that  such 
mirrors  reflect  the  solar  heat  quite  perfectly. 

82.  ABSORPTION  OF  HEAT.  —  Surfaces  are 

What     bodies 

absorb  heat  good  absorbers,  in  proportion  as  they  are 
poor  reflectors.  All  the  heat  that  falls  on 
any  surface,  must  be  either  reflected  or  absorbed.  In 
proportion,  therefore,  as  little  is  reflected  much  is  ab- 
sorbed. 

83.  ABSORPTION  CONTINUED.  —  Dark  cloth- 

What  effect  /•-,••,  •>         r 

has  color  on    ing  is  warmer  than  that  of  light  color,  for 


the  warmth  of    ^    reason   tfrat  heat  associated  with  light 

clothing  ? 

seems  to  follow  the  laws  of  the  latter  and 
undergo  absorption  or  reflection  with  it.  Now  we  know 
that  dark  objects  owe  their  dark  color  to  the  fact  that  they 
absorb  much  light,  and  reflect  but  little  to  the  eye.  Ex- 
periment shows  that  they  absorb  much  heat  also,  if  the 
heat  be  associated  with  light.  The  absorbed  light  must 
show  the  way,  as  it  were,  for  the  entrance  of  the  heat. 
Dr.  Franklin  proved  what  has  been  stated,  by  the  ob- 
servation that  when  different  colored  cloths  are  spread 
upon  snow,  it  melts  most  rapidly  under  those  which  are 
darkest. 

84.    EQUILIBRIUM    OF  TEMPERATURE.  — 

How  is  equili- 

brium  of  tem-  It  has  before  been  stated  that  heat  is  con- 
^11™^  Stantl7  radiated  from  all  bodies.  Absorp- 
tion of  heat,  is  also  universal.  If  any  num- 
ber of  bodies  are  equally  hot,  they  remain  so,  each  ac- 
cording to  its  surface,  imparting  to  the  rest  and  receiv- 
ing from  all  the  rest,  taken  together,  the  same  quantity 


RADIATION.  43 

of  heat.  If  one  is  hotter  than  the  rest,  it  gives  faster 
than  it  receives,  until  the  equilibrium  is  reached.  And 
if,  while  they  are  thus  coming  to  the  same  temperature, 
one  is  a  good  reflector,  and  therefore  slow  to  receive 
the  heat  which  comes  to  it,  it  is  also  slow  to  part  with 
what  it  gets ;  thus  the  difference  of  reflecting  power 
is  without  influence. 

85.  COOLING  OF  THE  EARTH. — Were  it 

slid**  of  the  not  f°r  the  SU11> tne  heat  °f  tne  earth  wollld 
cooling  of  the  waste  away  very  rapidly  into  space.  It  is, 

in  fact,  radiated  into  space  now,  as  truly 
as  if  there  were  no  sun  or  stars,  but  these  make  tip  for 
the  loss.  At  night,  when  the  sun  is  below  the  horizon, 
the  waste  by  radiation  takes  place  very  rapidly,  and 
the  earth  and  air  grow  colder  in  consequence.  It 
is  not  simply  because  of  the  absence  of  the  direct 
heat  of  the  sun,  for  this  is  removed  at  once  when  the 
sun  sets,  while  the  cooling  proceeds  until  morning. 
As  the  earth,  being  solid,  is  a  better  radiator  than 
the  air,  it  cools  most  rapidly,  sending  out  its  heat 
through  the  air  into  space.  In  this  way  the  earth  often 
becomes  cooled  from  ten  to  twenty  degrees  lower  than 
the  air  above  it. 

86.  ICE  IN  THE  TROPICS. — Advantage 

How  is  ice  pro-  ... 

duccd  in  the  is  taken  of  the  cooling  which  occurs  by  ra- 
trojncs?  diation,  to  produce  ice,  in  countries  where 

the  temperature  of  the  air  does  not  fall  to  the  freezing 
point.  Water  contained  in  shallow  vessels,  placed  in 
trenches  dug  in  the  ground,  to  protect  it  from  currents 
of  warm  air,  becomes  covered  with  ice  by  a  night's  ex- 


44  HEAT. 

posure.  That  the  water  is  not  frozen  by  evaporation,  is 
evident  from  the  fact  that  it  does  not  freeze  in  windy 
nights,  when  evaporation  is  greatest. 

87.  THE  FORMATION  OF  DEW. — Dew 
formation  of  does  not  "fall."  Its  deposition  is  an- 
other consequence  of  the  cooling  of  the 
earth  by  radiation.  The  air,  however  transparent,  al- 
ways contains  moisture,  absorbed  and  invisible.  Cold, 
causes  the  air,  like  every  thing  else,  to  contract,  and 
presses  out  of  it,  as  it  were,  the  water  which  it  con- 
tains. Now,  when  at  night  the  earth  has  become 
cooled  by  radiation,  the  warmer  air  which  comes  in 
contact  with  it  is  cooled,  and  thus  made  to  deposit  its 
moisture  in  the  form  of  dew.  When  the  temperature 
is  sufficiently  low,  the  dew  takes  the  form  of  frost. 

88.  WHY  CLOUDS  PREVENT  DEW. — Clouds 
prevent0  ™he  send  back  the  heat  radiated  from  the  earth, 
formation  of  -fry  a  new  radiation,  and  thus  prevent  the 
cooling  which  is  essential  to  the  produc- 
tion of  dew.  No  dew  is  found  therefore,  on  cloudy 
nights, '  when,  if  it  came  from  above,  like  rain  and 
snow,  we  should  expect  most. 

89.     ARTIFICIAL    PREVENTION    OF  DEW 

How   can    the  . 

formation  of    AND  FROST. — It  is  only  necessary  to  sub- 

stitute  for  clouds  the  artificial  canopy  of  a 
muslin  handkerchief,  or  any  other  cover- 
ing, at  a  little  distance  from  the  earth,  to  prevent  the 
deposition  of  dew  and  frost.  Gardeners  practised  this 
method  of  protecting  their  tender  plants  from  frost, 
long  before  philosophers  explained  it. 


RADIATION.  45 

90.   ABSENCE  OF  DEW  ON  POLISHED  SUR- 

"Why    is    dew 

not  '  deposited    FACES.  —  Dew  does  not  form  on  polished 


surfaces  because  they  are  poor  radiators,  or, 
in  other  words,  do  not  allow  their  heat  to 
escap'e,  and  thereby  produce  the  degree  of  cold  which 
is  required  to  form  dew.     Leaves  and  grass  receive 
most  dew,  because  they  are  the  best  radiators. 

91.  SUPPOSED    RADIATION   OF  COLD. — 

Why  does  the  . 

thermometer  li  a  piece  oi  ice  be  held  before  a  ther- 
broucht  "near  mometer>  ^  wn"l  cause  the  mercury  to  sink. 
ice?  It  is  not  because  cold  has  been  radiated 

from  the  ice,  but  because  the  thermometer,  in  common 
with  all  other  bodies,  is  constantly  giving  out  heat, 
and  when  the  ice  is  near,  it  does  not  get  its  due  portion 
in  return.  The  ice  cuts  off  the  heat  that  would  have 
come  to  it  from  other  objects  behind  it,  and  gives  it  but 
little  in  its  place. 

92.  REFRACTION    OF  HEAT. — Rays  of 

How  arc  rays 

of    heat    re-    heat  from  the  sun  and  other  objects,  are 
refracted  or  bent  out  of  their  course,  on 

passing  from  one  medium  to 

another,  similarly  to  rays  of 

light.       By     ordinary     glass 

prisms  most  of  the  heat  rays 

are  refracted  in  a  less  degree. 

93.    HEAT  RAYS  AND  CHEMICAL  RAYS. — 
The  light  which  proceeds  from  the  sun,  is 


rays  and  che-    accompanied  by  rays  of   heat  and  others 

mical  rays  ?  . 

called  chemical  or  actinic  rays.  In  the 
analysis  of  light  by  a  prism,  the  chemical  rays  accu- 
mulate principally  in  the  region  of  the  violet  color  of 


46  HEAT. 

the  spectrum,  while  the  most  of  the  heat  rays  are 
thrown  into  the  region  of  the  red,  and  below  it.  Nei- 
ther the  place  of  the  heat  rays  nor  the  chemical  rays 
is  visible  to  the  eye,  but  a  delicate  thermometer  proves 
that  there  is  most  heat  just  below  the  red,  and  a  piece 
of  paper  covered  with  chloride  of  silver,  (a  substance 
very  sensitive  to  the  chemical  rays  of  light,)  grows 
black  most  rapidly  in  the  region  of  the  violet.  The 
place  of  the  chemical  and  heat  rays  is  thus  shown,  al- 
though neither  can  be  seen.  It  is  not  to  be  understood 
that  they  are  confined  to  the  points  indicated,  but  only 
that  they  are  accumulated  there  in  largest  proportion. 

94.  BURNING  GLASSES.  —  The  collection 

action™  thof  of  raYs  of  heat  from  the  sun  by  ordinary 
burning  glass-  burning  glasses,  depends  on  the  fact  that 
they  are  refracted,  or  bent  out  of  their 
course  on  passing  from  one  medium  to  another,  pre- 
cisely as  in  the  case  of  light.  A  lens  made  of  two 
watch-glasses,  filled  with  water,  answers  for  heat  as 
well  as  light,  and  may  be  used  as  a  burning  glass. 

95.  DIFFERENT  HEAT  RAYS.  —  There  are 
ray*  of  heat    different  kinds  of  heat  rays,  as  there  are  of 

light  rays  ;  some  will  pass  through  one 
substance  best,  and  some  through  another.  Thus,  a 
piece  of  smoked  rock  salt  allows  the  blue  heat  ray  of 
the  spectrum  to  pass,  while  alum  lets  the  lower  or 
red  heat  ray  pass. 

96.  ANALYSIS  OF   HEAT.  —  The  analysis 

How     is     the 

analysis     of    ot  neat  is  enected.  by  the  same  means  as 

keate/eeteJf  are 


through  a  prism  just  as  if  light  were  to  be  analyzed, 


RADIATION.  47 

but  a  dark  colored  glass  is  previously  placed  before  the 
prism,  to  absorb  the  light  and  allow  the  heat  only  to 
pass.  Emerging  from  the  prism,  it  forms  an  invisible 
spectrum  of  rays  beyond.  These  rays  correspond  to 
the  different  colored  rays  of  light,  and  have  different 
capacities  of  passing  through  different  substances,  as 
before  stated.  But,  strictly  speaking,  they  have  no 
color  ;  they  were  called  blue  and  red,  simply  to  de- 
signate their  relative  position.  Heat  from  very  intense 
sources  is  mostly  violet,  and  violet  heat  passes  more 
readily  than  the  other  rays  through  most  substances. 
This  accounts  for  the  fact  that  the  heat  of  the  sun  is 
not  stopped  by  glass,  and  many  other  substances 
which  stop  the  heat  of  a  fire. 

97.  EFFECT  OF  DIFFERENT  HEAT  RATS 
xrid  of™  the  IN  MELTING  SNOW. — Snow  melts  compara- 
meiting  of  tively  slowly  in  the  heat  of  the  sun,  for 

snow?  J  J 

the  reason  mentioned  in  the  last  paragraph. 
Being  from  a  highly  heated  source,  it  passes  through 
the  snow  instead  of  stopping  to  melt  it.  But  near  a 
fallen  tree  melting  proceeds  more  rapidly,  because  the 
heat  absorbed  as  violet,  is  radiated  again  from  the  mod- 
erately heated  source  as  red  heat,  which,  falling  on  the 
snow  in-  its  vicinity,  is  readily  absorbed,  instead  of  be- 
ing transmitted. 

98.    BURNING  GLASS    OF    ICE. — A   lens 

How  can  gun- 
powder be  iff-    sufficiently  powerful  to  ignite  gunpowder 

may  even  be  made  of  ice.  In  using  any 
lens,  it  is  first  to  be  placed  near  the  object  to  be  ignited, 
and  then  withdrawn  till  the  spot  of  light  which  it 
casts  is  round  and  very  small.  The  focus  to  which 


48  HEAT. 

all  the  rays  of  light  converge  is  thus  found.  The  heat 
focus  is  a  little  beyond,  but  so  near  that  the  difference 
need  not  be  taken  into  account. 


Section  3. — Changes  effected  by  Heat. 

99.  EXPANSION,  MELTING,  AND  VAPORIZA- 
TION  are  the  principal  changes  effected  by 

heat?  heat,  while  contraction,  freezing,  and  con- 

densation of  vapor  are  produced  by  its  withdrawal. 
But  before  these  changes  are  explained,  it  will  be  well 
to  consider  certain  remarkable  differences  in  the  heat- 
ing effects  of  heat,  in  the  case  of  different  substances. 

100.  THE     HEATING    EFFECT  OF   HEAT  IS 

Are  the  effects    DIFFERENT    FOR    DIFFERENT    SUBSTANCES. 

of  neat   equal 

in  different  It  might  naturally  be  supposed  that  the 
same  quantity  of  heat  actually  imparted 
to  different  substances  would  make  them  equally  hot ; 
but  this  is  not  the  case.  If  two  cannon  balls  of  the 
same  size,  and  at  the  same  temperature,  are  quenched, 
the  one  in  mercury  and  the  other  in  water,  the  mer- 
cury will  be  made  much  hotter  than  the  water,  by 
the  reception  of  the  same  amount  of  heat.  It  does 
not  simply  feel  hotter,  as  it  might  do  if  it  were  not 
really  so,  from  the  superior  conducting  power  of  the 
mercury,  but  it  is  actually  so,  as  may  be  ascertained 
by  testing  the  temperature  by  the  thermometer. 
What  is  sped-  101-  SPECIFIC  HEAT. — If  the  above  ex- 
fic  heat  ?  periment  were  varied,  by  quenching  in 
mercury  a  bullet  of  one-thirtieth  the  size  of  that  used 


SPECIFIC    HEAT.  49 

for  the  water,  the  two  would  be  brought  to  the  same 
temperature.  In  other  words,  mercury  requires  but 
one-thirtieth  as  much  heating  as  water,  to  make  it 
equally  hot.  It  fills  up,  as  it  were,  with  heat,  more 
rapidly.  The  comparative  quantity  required  by  each 
substance  is  called  its  specific  heat. 

102.  Taking  water  as  the  standard,  and 
calling  its  specific  heat  one,  that  of  mer- 


mercury?   Of  Cury  is  about  one-thirtieth.     That  of  iron 
is  about  one-tenth.     The  specific  heat  of 
other  substances  is  given  in  decimals  in  a  table  con- 
tained in  the  appendix. 

What  is  capa-  103.  CAPACITY    FOR    HEAT.  -  If  We  COm- 

dty  for  heat  ?  pare  equai  {mlks  of  water  and'  mercury, 
instead  of  equal  weights,  AVC  make  out  the  specific 
heat  of  mercury  to  be  one-half  instead  of  one-thirtieth. 
The  comparison  is  sometimes  made  in  this  way,  but 
the  term  capacity  for  heat,  instead  of  specific  heat  is 
always  employed  in  such  cases.  Thus,  we  say  that 
water  has  twice  the  capacity  of  mercury  for  heat. 
,„,  .  .  ..  104.  RELATION  OF  HEAT  AND  DENSITY. 

W  liat  relation 

exists  between    If  water  were   suddenly    converted   into 

density       and  ,      ,  -i  -i    -i 

capacity  for  niercury,  much  heat  would  be  given  out, 
heat?  as  js  evident  from  what  has  already  been 

stated.  So  when  a  metal  is  hammered,  the  capacity 
of  the  denser  metal  for  heat  being  less,  the  surplus 
goes  to  make  it  sensibly  hotter.  In  other  words,  in 
proportion  as  density  is  increased  in  any  substance,  its 
capacity  for  heat  is  diminished,  and  vice  versa.  It  is 
not,  however,  to  be  understood  that  the  comparative 
capacity  for  heat  in  different  substances  is  always  in 

3 


50 


HEAT. 


proportion  to  their  density  ;  this  is  by  no  means  uni- 
versally the  case. 

105.     THE    OCEAN    A    RESERVOIR   AND 

How   does  the 

ocean  serve  as     REGULATOR   OF  HEAT. In  hot  Weather  the 

a        reservoir  -L        -L      >i        i  c  ±-\          •          if    • 

and  regulator  ocean  absorbs  the  heat  of  the  air.  If  it 
of  heat?  were  an  ocean  of  mercury,  it  would  soon 
grow  as  hot  as  the  air,  and  therefore  cease  absorbing  • 
but  its  capacity  for  heat  is  so  much  greater  that  this 
does  not  occur.  Again,  in  cold  weather,  it  is  con- 
stantly giving  out  the  large  quantity  it  has  absorbed, 
but  at  the  same  time  itself  grows  cool,  though  very 
slowly.  It  is  thus  a  reservoir  of  heat  and  a  regulator 
of  climate. 

106.  FIRE  BY  COMPRESSION. — The  fire 
principle  of  svringe>  represented  in  the  figure,  is  an 
the  Fire  Sy-  instrument  designed  to  produce  fire 
by  the  compression  of  air.  On  forcing 
the  piston  suddenly  down,  the  tinder  below  it  is 
ignited.  This  takes  place  on  the  principle  already 
explained.  The  specific  heat  of  compressed  air 
is  less  than  that  of  air  uncompressed.  When  the  com- 
pression takes  place,  the  surplus  elevates  the  tempera- 
ture and  inflames  the  tinder. 


EXPANSION. 

107.  EXPANSION  UNIVERSAL. — All  bodies, 

ha*  athea/eon    solid>  liquid,  and  gaseous,  expand  by  heat, 

dun"?*  °^  b°~    and  contract  to  tneir  original  dimensions  on 

cooling.     An  iron  wire  lengthens  by  heat : 

the  mercury  in  a  thermometer  expands  and  rises  by 


EXPANSION.  51 

heating  ;  air  partially  filling  a  bladder  expands  and  fills 
it  by  the  operation  of  the  same  cause. 

108.  HOW  HEAT  EXPANDS  BODIES.  -  Heat 

How  does  heat 

operate  to  ex-    operates  to  produce  expansion,  by  insinua- 

pand  bodies?      tmg    itself  between    the    particles    of  Sllb- 

stances  and  increasing  their  distance  from  one  another. 
The  cooling  process  is  simply  a  removal  of  heat, 
which  allows  the  particles  to  assume  their  original  dis- 
tances from  one  another,  in  obedience  to  the  attraction 
of  cohesion. 

109.   EXPANSION  OF   SOLIDS.  —  The  ex- 

Among  solids,  .  .  • 

which  expand  pansion  of  solids  by  heat  is  comparatively 
the  most?  smalL  Among  Solids,  the  metals  expand 
the  most  ;  but  an  iron  wire  increases  only  ^^2  in 
length  on  being  heated  from  zero  up  to  212°.  Ex- 
pansion in  general  bulk  is  about  three  times  as  great 
as  in  length.  Thus,  a  cannon  ball  heated  to  212° 
would  occupy  about  zj-o  niore  space  than  when  cooled 
down  to  zero. 

110.  ILLUSTRATION.  —  The  expansio-n  of 


metals    be    U-     "be    lllustra- 
lustrated  ?  , 

ted    by  ar- 

ranging a  brick,  a  knit- 
tirig-needle.  and  a  shin- 
gle, as  in  the  figure.     On 
heating  the  needle  with  a  spirit  lamp,  the  shingle,  if 
before  carefully  poised,  will  be  overturned. 
What    appli-  11L     WHEEL-TIRES,    RIVETS,    ETC  — 

cation  of  this    Important  application  of  even  this  small 

expansion     ts  .          . 

made  in  the    degree  of  expansion  is  made  in  the  arts. 
t|reg  Q£  carrjage  wheels,  for  example, 


52  HEAT. 

are  made  originally  too  small  for  the  frames  they  are 
to  surround..  They  are'  then  heated  red  hot  and  ap- 
plied in  a  state  of  expansion.  The  contraction  which 
afterward  takes  place,  on  sudden  cooling  hy  cold  wa- 
ter, binds  the  wooden  frame-work  together  with  the 
greatest  firmness.  So  in  making  steam-boilers,  the 
rivets  are  fastened  while  hot,  that  they  may  by  subse- 
quent contraction  unite  the  plates  more  firmly. 

112.  HOT-WATER   PIPES.  —  In     certain 

What    disad-  .  .  .     ^ 

vantages  arise  uses  to  which  iron  is  applied,  the  conse- 
^ansion.6  o/*~  (luences  °^  expansion  have  to  be  carefully 
metals?  guarded  against.  A  cast-iron  pipe  for  the 

conveyance  of  steam  or  hot  water,  must  not  be  so  laid 
that  its  ends  touch  two  opposite  walls,  lest  by  its  ex- 
pansion when  heated,  the  walls  should  be  overturned. 

113.  CLAMPS  IN  WALLS.  —  If   the  two 

ends  of  a  Piece  of  metal  are  fixed  so    that 


clamps       in   they  cannot  move,  and  contraction  takes 

walls  ? 

place  by  cold,  the  metal  must  break.  Cast- 
iron  clamps  in  walls  are  frequently  thus  broken.  If 
they  are  of  wrought  iron,  they  often  crush  the  stone, 
and  thus  loosen  themselves  in  their  sockets. 

114.  LIFTING  WALLS.  —  Walls  of  build- 

Mow  are  walls 

straightened  ings  in  danger  of  falling,  have  been  restored 
b<Ld€XPcontr™-  to  tnen*  perpendicular  position  by  taking 
tion?  indirect  advantage  of  expansion.  This 

is  eifected,  by  connecting  the  walls  to  be  lifted  into 
place,  by  an  iron  rod,  fixed  firmly  into  one  wall,  and 
passing  loosely  through  a  hole  in  the  other.  The 
whole  length  of  the  rod  is  then  heated  by  lamps, 
whereby  expansion  is  occasioned,  and  the  rod  made  to 


EXPANSION.  53 

project  beyond  the  building.  The  nut  with  which  it 
is  provided  is  then  screwed  up  on  the  projecting  rod, 
until  it  touches  the  outside  of  the  wall.  The  lamps 
being  then  removed,  the  rod  cools,  and,  by  its  con- 
traction, draws  up  the  walls  with  it. 

115.  FRACTURE  OF  GLASS  VESSELS. — 
fracture  of  Glass  expands  less  than  iron  by  heat,  yet 
glass  vessels  sufficiently,  when  expansion  is  unequal  on 

by  heat?  ''  H 

opposite  surfaces,  to  occasion  its  fracture. 
Thus  if  hot  water  be  poured  on  a  thick  glass  plate,  it 
cracks.  The  first  effect  is  to  expand  the  upper  surface, 
while  the  under  one  is  but  slightly  affected.  The  ob- 
vious tendency  of  this  unequal  expansion,  is  to  warp 
the  plate,  and  curve  it  inward  toward  the  under  side. 
But,  as  the  glass  cannot  bend,  it  breaks. 

116.     HOW    TO    CUT    GLASS    BY  HOT   WIRE. 

How  can  heat 

be  used  to  cut    In  consequence  of  the  same  unequal  expan- 


sion, a  crack  once  commenced  in  glass  may 
be  made  to  follow  the  heated  end  of  a  rod  of  iron  or  pipe- 
stem  drawn  over  its  surface.  Broken  vessels  of  glass 
may  be  thus  cut  into  useful  shapes.  A  glass  vial  may 
be  cut  evenly  in  two,  by  encircling  it  with  a  ring  of 
iron  heated  to  redness,  and  afterward  plunging  it  into 
cold  water.  The  glass  beneath  the  ring  becomes  ex- 
panded through  and  through,  and  the  subsequent  im- 
mersion in  water,  causes  a  sudden  contraction  in  the 
exterior,  and  consequent  fracture,  on  the  principle  above 
stated. 

117.    WOOD    AND    MARBLE    EXPAND    LIT- 

TLE.^-Wood  and  marble  expand  but  little 


used  for  pen-    "by  heat,  and  are  therefore  sometimes  used 
dulum  rods  ?  ' 

for  pendulum  rods,  where  careful  provision 


54 


HEAT. 


must  be  made  against  change  of  length  by  change  of 
weather. 

118.     LIQUIDS    EXPAND    MORE    THAN    SOL- 

IDS.—  A  column  of  water  inclosed  in  a  glass 
sion  of  water  tube,  will  expand  aV  in  length  on  being 

heated  from  freezing  to  the  boiling  point 
of  water,  while  a  column  of  iron  will  expand  only  ^l^. 

119.  ILLUSTRATION.  —  The  overflow  of 
Illustrate    the 

expansion  of  water  from  full  vessels  before  boiling 
liquids  by  heat.  commenceSj  so  often  observed  in  the 

kitchen,  is  in  consequence  of  expansion  by  heat.     To 

illustrate   the    expansion    of   liquids,   a 

test-tube  full   of  water  may  be  heated 

over  a  spirit  lamp,  as  indicated  in  the 

figure.     The    water   will    be  found  to 

heap  itself  into   a  convex  surface  over 

the  mouth  of  the  tube,  and  even  to  run 

over,  long  before  boiling  commences. 

120.  COLD    WATER  EX- 

What  effect 

PANDS    BY    COLD.  -  There    is 

an  important  exception  to  the  general  law 
of  expansion  of  liquids  by  heat  and  contraction  by  cold, 
or  withdrawal  of  heat.  Very  cold  water  (39  F.  )  expands 
by  further  cold  before  it  freezes.  Again,  on  conver- 
sion into  ice,  it  undergoes  still  further  expansion. 

12  1  .  ILLUSTRATION.  —  Expansio  n  by  these 

How  may  ex- 

pansionbycoid   combined  causes  may  be  shown  by  bury- 

be  illustrated?     ing  ft  tegt.tube  full  of  water  m  a  mixtllre  of 

snow  and  salt.  Before  the  water  is  completely  frozen, 
it  will  rise  at  least  a  quarter  of  an  inch,  and  fill  the 
tube.. 


has    cold  on 

' 


EXPANSION.  55 

The  greaterpart  of  this  expansion  is  owing  to 
the  latter  of  the  causes  above  mentioned.  The 
freezing  mixture  employed  is  made  of  two 
parts  snow    to    one   part  salt,  brought   into 
the    cup  alternately,  in  small   portions.     It 
is  well  to  wrap  the  cup  in  flannel,  or  other 
cloth,  to  prevent  loss  of  heat.     From  ten  to  fifteen 
minutes  are  required  for  the  experiment.     If  the  water 
is  perfectly  frozen,  the  tube  will  be  cracked  by  its  ex- 
pansion. 

122.    COLD  WATER  FLOATS  ON  WARMER 

coldwaterfoat     WATER    AN»    PROTECTS    IT.— It  Was   shown 

on  warmer  wa-  in  the  last  paragraph  that  very  cold  water 
(below  39°)  is  in  an  expanded  condition, 
and  occupies  more  space  than  warmer  water.  It  fol- 
lows that  it  is  lighter,  arid  will  float  on  warmer  water. 
As  the  weather  grows  colder  each  winter,  and  the  time 
approaches  for  the  formation  of  ice,  in  rivers  and  lakes 
the  cold  water  does  actually  float  on  the  warmer,  on  a 
grand  scale,  and  protect  it  from  the  cold.  The  body 
of  water  being  thus  protected,  ice  never  forms  many 
feet  thick.  The  case  would  be  very  different  if  water 
grew  constantly  heavier  by  cold.  The  surface  water 
would  then  constantly  sink,  until  all  were  reduced  to 
the  freezing  point.  Cooling  does,  in  fact,  proceed  in 
this  way  until  the  temperature  sinks  to  39° ;  then  the 
exception  comes  in  play,  and  the  surface  water,  as 
before  stated,  retains  its  place  and  exerts  its  protecting 
influence.  When  ice  is  subsequently  formed  it  has  the 
same  effect. 


56  HEAT. 

123.  CONSEQUENCES  OF  THE  LIGHTNESS 

WJtat     conse-  r>          ,, 

qucnces  remit     OF    VERY    COLD     WATER. But     lOI     the    16- 

from  the  ex-    markable  fact  that  more  cold  makes  very 

pansion  of  wa- 
ter by  cold  ?       cold  water  lighter,  and  not  heavier,  and 

thus  enables  it  to  exert  the  protecting  influence  just 
explained,  the  cold  of  a  single  winter  would  be  suffi- 
cient to  kill  all  the  fishes  inhabiting  our  lakes  and 
rivers.  Another  consequence  would  be  change  of  cli- 
mate, as  a  necessary  result  of  the  formation  of  im- 
mense masses  of  ice,  which  the  heat  of  the  summer 
would  be  insufficient  to  melt.  The  temperate  regions 
of  the  earth  would  thus  become  uninhabitable.  Such 
are  the  consequences  which  are  obviated  by  this 
remarkable  exception  to  a  general  law  of  expansion. 
The  whole  realm  of  nature  furnishes  no  more  remark- 
able evidence  of  design  on  the  part  of  the  CREATOR. 

124.  SOME  LIQUIDS  EXPAND  MORE  THAN 

In  what  pro- 
portion do  spi-    OTHERS. — Some  liquids  expand  more  by 

Toil,ald  water  heat  than  others.  Spirits  of  wine,  on  be- 
expand?  jng  heated  from  32°  to  212°,  increases  one- 
ninth  in  bulk  ;  oil  expands  about  one-twelfth,  and  wa- 
ter, as  has  before  been  stated,  one-twenty-third.  It  is 
much  to  the  advantage  of  the  dealer  in  spirits  to  buy 
in  winter  and  sell  in  summer.  Twenty  gallons 
bought  in  January,  will  have  become,  by  expansion, 
twenty-one  in  July.  The  difference  between  the  cold- 
est and  warmest  weather  of  the  year,  is  sufficient  to 
make  about  this  difference  in  bulk. 

How  do  gases  125'    GASES    EXPAND  M°RE  THAN  EITHER 

compare  with    SOLIDS  OR  LIQUIDS. — Gases  expand  more 

solids  and  li-       ,  .  , 

quids  in  ex.    tnan  either  solids  or  liquids  by  heat.     The 
t      reason    is,   that  in    gases  there  is  no  co- 


EXPANSION.  57 

hesion  to  overcome,  as  in  the  two  other  states  of 
matter.  While  iron  increases  in  general  bulk  ^y^th. 
and  water  about  ^Vd,  on  being  heated  from  the  freez- 
ing to  the  boiling  point  of  the  latter,  air  expands  more 
than  Jd  by  the  same  increase  of  temperature. 

126.    LAW     OF    EXPANSION    FOR    GASES. 

State    the  law 

of  expansion  Gases  expand  ^oth  of  the  bulk  which  they 
for  gases.  possess  at  32°, for  every  degree  above  that 
point,  and  contract  in  the  same  proportion  for  every  de- 
gree below  it.  Thus,  490  cubic  inches  at  32°  would 
so  expand  as  to  occupy  an  inch  more  space  at  3-3°, 
still  another  inch  at  34°,  and  at  the  same  rate  for 
higher  temperatures.  And  the  same  quantity  would 
contract  by  cold,  or  withdrawal  of  heat,  so  as  to  oo 
cupy  an  inch  less  space  at  31°,  and  two  inches  less  at 
30°,  and  so  on  for  lower  temperatures.  The  law  is 
the  same  for  steam  and  other  vapors. 
What  is  a  127.  THE  THERMOMETER. — The  ther- 
thermometer  ?  niometer  is  an  instrument  in  which  ex- 
pansion is  made  use  of  to  show  changes  of  tem- 
perature. A  straight  wire,  which  would  grow  regu- 
larly and  perceptibly  longer  in  proportion  to  the 
increase  of  temperature,  would  form  the  most  conve- 
nient thermometer.  But  solids  do  not  expand  enough, 
or  with  sufficient  regularity,  for  this  purpose.  The 
liquid  metal  mercury,  is  therefore  employed  instead, 
being  inclosed  in  a  glass  tube  and  bulb. 

128.     MANUFACTURE     OF     THERMOME- 

How  are  ther- 

mometcrsman-    TERs. —  In     making     thermometers,    the 

mercury   being   first  introduced  into  the 

bulb,  is  boiled,  so  as  to  expel  all  air  and  moisture, 

3* 


58  HEAT. 

and  fill  the  tube  with  its  own  vapor.  As  the  metal 
cools,  it  contracts  and  collects  in  the  "bulb  and  lower 
part  of  the  tube,  leaving  a  vacuum  above.  The 
end  of  the  tube  being  then  closed  by  fusion,  the 
instrument  is  complete,  with  the  exception  of  grad- 
uation. Used  in  this  condition,  the  mercury  would 
be  observed  to  rise  and  fall  with  changes  of  tempe- 
perature,  but  we  should  not  be  able  to  say  how  much 
or  how  little. 

129.  GRADUATION  OF  THERMOMETERS.  — 
thermometers  To  obtain  a  fixed  point  from  which  to 
graduated/  count,  the  instrument  is  immersed  in  melt- 
ing ice,  and  the  point  to  which  the  mercury  sinks 
scratched  on  the  glass.  This  point  is  called  zero. 
Another  fixed  point  is  obtained  by  immersing  the 
thermometer  in  boiling  water,  and  when  the 
mercury  has  risen,  noting  this  height  also  on 
the  glass,  and  marking  it  100°.  The  space  be- 
tween the  two  points  is  next  divided  into  one 
hundred  equal  parts,  by  scratches  on  the  glass, 
and  numbered  from  one  up  to  a  hundred.  The 
upper  and  lower  portions  of  the  tube  are  marked 
off  into  divisions  of  the  same  length,  for  very 
high  and  low  temperatures. 

CENTIGRADE    THERMOMETER. 


Describe     the 

Centigrade        A  thermometer  graduated   as  above 
is  called  a  centigrade  thermometer, 


from  th  e  fact  that  the  space  between  <  '  boiling  '  '  and    ^ 
"  freezing"  is  divided  into  one  hundred  degrees.     This 
is   by  far  the  most  rational  method   of   graduating, 
and  these    thermometers  are  in  general  use    on   the 


THE    THERMOMETER. 


59 


continent  of  Europe,  and  by  scientific  men  all  over 
the  world. 

131.  FAHRENHEIT  THERMOMETER. — This 

Describe     the     . 

Fahrenheit  is  the  thermometer  in  common  use  in  this 
thermometer.  country.  The  iristrument  itself  is  pre- 
cisely the  same  as  the  centigrade.  The  difference  is 
only  in  the  graduation.  In  graduating  it,  the  space 
between  the  freezing  and  boiling  points  having  been 
marked  on  the  glass,  is  divided  into  one  hundred  and 
eighty  parts,  and  the  rest  of  the  tube,  above  and  below, 
into  similar  spaces.  The  zero,  or  starting  point,  is 
fixed  lower  down  than  in  the  centigrade, 
where  nothing  especial  happens,  instead  of 
where  water  freezes.  The  consequence  is, 
that  in  counting  up  and  affixing  the  numbers? 
the  freezing  point  comes  at  32°,  and  the 
boiling  point  at  212°.  There  is  no  good  rea- 
son for  placing  the  zero  there,  or  for  qhoosing 
such  a  number  as  180  for  the  number  of  de- 
grees between  freezing  and  boiling.  The 
centigrade  graduation  is,  therefore,  much  to 
be  preferred.  If  a  thermometer  of  each 
kind  were  immersed  in  boiling  water,  the 
mercury  would  rise  in  the  centigrade  to  the 
point  marked  100,  and  in  the  Fahrenheit  *^  ^^ 
to  the  point  marked  212.  In  the  same  way,^ero  cen- 
tigrade corresponds  to  32°  Fahrenheit.  The  two  ther- 
mometers are  compared  in  the  figure. 

ff oio  is  extreme  132.      EXTREME    COLD,     HOW    MEASURED. 

coidmeasurcd?    AS  the  temperature  is  lowered,  the  mer- 
cury of  the   Fahrenheit  thermometer  sinks,  until  by 


60  HEAT. 

sufficient  cold  it  reaches  39  degrees  below  zero. 
There,  intense  cold  has  no  effect  upon  it,  for  at  this 
point  the  mercury  freezes.  How  much  colder  it  is 
than  39°  cannot  be  told,  therefore,  by  the  mercurial 
thermometer.  Thermometers  containing  alcohol  in- 
stead of  mercury  are  used  for  this  purpose,  because  al- 
cohol never  freezes,  and  will  continue  to  sink  further 
and  further  in  the  tube  the  colder  it  grows. 

133.    EXTREME   HEAT,  HOW  MEASURED. 

How  is  extreme 

heat  meas-  If  a  Fahrenheit  thermometer  is  heated, 
the  mercury  in  it  rises, till  it  reaches  662°, 
and  then  begins  to  boil.  A  little  more  heat  forms  suf- 
ficient vapor  of  mercury  to  burst  the  tube.  For  this 
reason,  a  mercurial  thermometer  cannot  be  used  to 
measure  extreme  heat.  A  platinum  bar  inclosed  in  a 
black  lead  tube  shut  at  the  bottom,  is  common- 
ly employed  for  this  purpose.  Tube  and  bar  are 
placed  on  the  fire,  or  in  the  melted  metal,  whose 
heat  it  is  desired  to  measure,  one  end  being  left 
out,  so  that  it  can  be  seen.  The  consequence  is 
that  the  platinum  bar  expands,  and  projects 
from  the  earthen  tube.  The  tube  itself  expands  but 
little.  The  further  the  bar  projects,  the  greater  is  the 
heat.  As  it  pushes  out,  it  is  made  to  move  an  index 
hand,  and  point  to  the  number  indicating  the  tempera- 
ture, on  a  graduated  arc.  This  arc  is  first  graduated  by 
repeated  trials,  observing  how  much  the  bar  projects 
and  moves  the  hand  by  the  same  heat  which  raises 
the  mercury  one  degree  in  the  Fahrenheit  thermometer. 

n      .,      .,  134.   THE  AIR  THERMOMETER. — A  col- 

Describe     the  , 

air  thermome.-  umn  of  air  confined  in  a  glass  tube  over 
***'  colored  water,  was  the  first  thermometer 


LIQUEFACTION.  61 

used.  Heat  expands  the  air  and  lengthens  the  column 
downward,  pushing  the  water  before  it,  while  cold  has 
the  contrary  effect.  The  temperature  is  thus  indicated 
by  the  height  at  which  the  water  stands. 

135.  ILLUSTRATION. — The  principle  of 
^incTll  *o/  the  air  thermometer  may  be  illustrated  as 
the  air  ther-  represented  in  the  figure.  A 

mometer.  ^    ,         .       ,     ,,,     -.„     ,  , 

test-tube    is   half  filled,  and 
then  inverted  in  a  glass  of  water  without 
allowing  the  water  which  it  contains  to 
flow  out.     Heat  applied  to  the  tube  will  lengthen  the 
column  of  air  by  expansion. 


LIQUEFACTION. 
136.  SOLIDS  BECOME  LIQUIDS  BY  HEAT. 

flow  do  sohds 

become  li-  m  On  being  heated  up  to  a  certain  point,  solids 
quids?  are  jilted,  or  converted  into  liquids. 

Thus,  at  all  temperatures  below  32°,  water  is  solid 
ice,  but  the  moment  it  is  warmed  up  to  this  point, 
by  change  of  weather  or  other  means,  it  begins  to 
melt.  The  temperature  at  which  this  change  occurs 
is  called  the  melting  point.  32°  is  therefore  the  melt- 
ing point  of  ice.  The  melting  point  of  sulphur  is 
226°,  and  of  lead,  612°. 

137.   ALL  SUBSTANCES  ARE  FUSIBLE. — 

Are   all    sub- 
stances   fusi-    All    substances    are    fusible,  or,  in    other 

words,  may  be  melted ;  but  the  melting 
point  of  all  is  not  definitely  known.  Thus  carbon  has 
been  fused  by  the  heat  of  the  galvanic  battery,  but  it 
is  impossible  to  state  the  melting  point  in  degrees. 


62  HEAT. 

Under  great  pressure,  increased  heat  is  required  to  ef- 
fect fusion.     Thus  the  melting  point  of  sulphur  is 
raised  from  226°  to  285°,  by  a  pressure  of  11,880  Ibs. 
to  the  square  inch. 
nrj  .  138.   DISAPPEARANCE  OF  HEAT  IN  MELT- 

Wtiat  remark- 
able   drcum-    TNG. — Melting  or  fusing  is  effected  by  heat, 

stance  attends 

the  melting  of  and  a  remarkable  circumstance  attending 
it,  is  the  disappearance  of  the  heat  which 
has  effected  the  change.  Thus,  if  a  thermometer  be 
applied  to  ice  or  snow  which  has  just  begun  to  melt, 
it  will  be  found  to  stand  at  32°.  Let  the  ice  be  then 
introduced  into  a  tumbler,  and  placed  on  a  stove,  and 
the  temperature  again  tested  at  the  moment  when  the 
conversion  into  water  is  completed.  The  thermometer 
will  be  found  again  to  stand  at  32°.  The  water  produced 
is  no  hotter  than  the  original  ice,  yet  heat  has  been  pour- 
ing into  it,  through  the  bottom  of  the  ves- 
sel,during  the  whole  process  of  melting. 
If  a  piece  of  glass  of  the  same  size  had 
been  subjected  to  the  same  heat,  it  would 
have  grown  constantly  hotter.  It  fol- 
lows that  in  the  case  of  the  ice  there 
has  been  a  disappearance  of  heat.  This 
disappearance  always  occurs  whenever 
a  solid  is  converted  into  a  liquid. 

What       other  ^9.      ANALOGOUS      DISAPPEARANCE      OF 

{£appTarance  ACIDITY-—  Chemistry  furnishes  other  in- 
does  chemistry  stances  of  disappearance,  which  may  help 
us  in  understanding  this  one.  If  vinegar 
be  poured  upon  chalk  it  loses  its  sourness.  It  is  be- 
cause a  combination  has  taken  place  between  the  acid 


FREEZING    POINT.  63 

vinegar  and  the  lime  which  the  chalk  contains,  and  a 
new  substance,  called  a  salt,  has  been  formed  out  of 
both.  So  in  the  present  case,  we  may  suppose  that 
heat  and  the  solid  have  combined  to  form  a  liquid,  and 
the  property  of  heat  to  effect  the  senses  and  the  ther- 
mometer, has  at  the  same  time  disappeared.  Any  liquid 
may  therefore  be  regarded  as  a  compound  of  solid  and 
heat.  The  heat  which  thus  disappears  is  called  com- 
bined, or  latent  heat. 

Mention  some  140.  FREEZING  MIXTURES.  -  When  Solids 

feezing  mix-    take  a  liquid  form  by  other  means,  as.  for 

tures.    How  do  **  ;. 

they  produce  example,  when  salt  dissolves  in  water,  the 
temperature  is  generally  much  reduced. 
Nitre,  for  example,  reduces  the  temperature  of  water  in 
which  it  is  dissolved  from  15  to  18  degrees,  and  is  there- 
fore much  used  in  the  East,  where  it  is  abundant,  for 
cooling  wines.  Mixed  nitre  and  sal-ammoniac  have  a 
still  greater  effect.  Sulphate  of  soda  drenched  with 
strong  muriatic  acid,  will  reduce  the  temperature  from 
50°  to  zero. 

141.  When  two  solids,  on  being  mixed, 

Mention  other     .     . 

freezing  mix-    become  both   liquid,  still  greater  cold  is 
often    roduced-     Tnis  is  the  case  witn  a 


duce  greater  mixture  of  snow  with  common  salt,  or  with 
chloride  of  calcium.  By  the  former  mix- 
ture, used  as  shown  in  paragraph  121,  ice  cream  is 
frozen.  By  the  latter  mixture,  a  cold  sufficient  to  freeze 
mercury  may  readily  be  produced.  For  this  purpose, 
three  parts  of  the  salt  are  to  be  mixed  with  two  of  dry 
snow. 


64  HEAT. 

142.   THE  MELTING  OF  SNOW  COOLS  THE 

How  docs  the          — Whenever  ice  is  converted  into  wa- 

inelting   of 

snoiv  affect  the  ter,  whether  rapidly  by  fire  or  slowly 
by  change  of  weather,  the  disappearance 
of  heat,  above  mentioned,  occurs.  Thus,  when  the 
snow  melts  in  spring,  heat  is  drawn  off  from  the  air 
and  made  latent,  or  combined  in  the  water  which  re- 
sults from  the  melting.  This  makes  the  weather 
cooler  than  it  would  otherwise  be,  and  retards  in  a 
measure  the  advance  of  spring. 

How  do  liquids  143.  FREEZING. — Liquids  become  solids 
become  solids?  ^y  t}ie  removal  of  their  combined  heat. 
Thus,  if  molten  lead  be  allowed  to  stand  awhile,  the 
heat  which  it  contains  passes  away  into  other  objects, 
warming  them ;  and  the  metal  itself,  having  lost  its 
heat,  becomes  solid.  So  in  winter,  the  combined  heat 
which  is  contained  in  water,  is  conveyed  away  by  the 
colder  air,  and  the  water,  having  lost  its  heat,  is  con- 
verted into  ice. 

144.  FREEZING   POINT. — The   tempera- 

What    is    the  L 

freezing  point    ture  at  which  a  substance  passes  from  the 

of  a  liquid?        liquid    into    the     golid    gtate     ig    called    the 

freezing  point.  Thus,  32°  is  the  freezing  point  of  wa- 
ter. The  freezing  point  of  any  substance  is,  as  might 
be  supposed,  the  same  as  the  melting  point.  Water,  for 
example,  becomes  ice  in  process  of  cooling,  at  the 
same  temperature  that  ice  becomes  water  in  process  of 
heating. 

145.  ALL  LIQUIDS  HAVE  THEIR  FREEZ- 

Can .all  liquids 

be  frozen?         ING  POINTS. — There  is  good  reason  to  be- 

Give  examples.    ^Q    ^    ^    ^.^  without    exception> 


L  AT  E NT     U  R  AT.  65 

have  their  freezing  points,  but  the  reduction  of  tem- 
perature requisite  has  not  in  the  case  of  all  been  at- 
tained. Alcohol  and  ether,  for  example,  have  never 
been  frozen. 

146.      IN    FREEZING,     LATENT     HEAT    BE- 
whatfrbecomes     COMES  SENSIBLE   HEAT.— If   Water,  in  Sllffi- 

of  the  latent  cient  quantity,  be  taken  into  an  apartment 
whose  temperature  is  several  degrees  be- 
low the  freezing  point,  and  then  allowed  to  become 
ice,  it  will  be  found  that  the  freezing  process  has  ac- 
tually warmed  the  apartment  several  degrees.  The 
latent  heat  has  been  drawn  off  by  the  colder  air  of 
the  room,  raising  its  own  temperature,  and  leaving  the 
water  in  the  condition  of  ice. 

147.  CELLARS  WARMED  BY  ICE. — In  ac- 

How  can  cel- 
lars be  warmed    cordance  with  the  principle  above  stated, 

tubs  of  water  are  sometimes  set  to  freeze 
in  cellars,  thereby  to  prevent  excessive  cold.  And 
even  in  the  coldest  climates  a  sufficient  supply  of  wa- 
ter might  thus  be  made  to  secure  an  apartment  against 
extreme  cold. 

148.  EFFECT  ON  CLIMATE. — The  milder 
ha%afhe  free*-    climate  of  the  vicinity  of  lakes  which  are 
ing  of  water    accustomed  to  freeze  in  winter,  and  the 

on  climate  ?  ~     .  ,      . 

moderation  of  the  weather  during  a  snow 
storm,  are  accounted  for  on  the  same  principle.  As  the 
melting  of  snow  retards  in  a  certain  degree  the  ad- 
vance of  spring  by  the  heat  it  abstracts  from  the  at- 
mosphere, so  the  formation  of  ice  tends  to  make  the 
advance  of  winter  less  rapid,  by  the  heat  which  it 
evolves. 


66  HEAT. 

CHAPTER  VII. 

VAPORIZATION. 
149.    FORMATION    OF    VAPORS. — While 

Do    vapors  .  . 

form  at    all    melting,  or  the  conversion  of  a  solid  into 

temperatures?     a  liquid)    occurs    only    when    the     solid    is 

heated  up  to  a  certain  fixed  point,  the  conversion  of  a 
liquid  into  a  vapor  takes  place  at  all  temperatures. 
Thus  water  is  always  passing  off  into  vapor  from  the 
surface  of  the  ocean,  and  from  the  moist  earth. 

150.  VAPORS  TRANSPARENT. — All  vapors 

What   is    the 

appearance  of  are  perfectly  transparent,  like  the  atmo- 
sphere. If  water  be  boiled  in  a  flask,  it 
will  be  found  that  the  steam  within  the  flask  is  as 
transparent  as  air.  The  steam  thrown  from  a  locomo- 
tive would  be  invisible  if  it  remained  steam  We 
should  hear  its  roar,  but  see  nothing. 

151.  DENSITY  OF  VAPORS. — Vapors  are 

/«  the  density 

of  vapors  uni-    of  all  degrees  of  density.     The  vapor  of 
water  may  be  as  thin  as  air,  or,  again,  al- 
most as  dense  as  water  itself. 

152.   ELASTICITY  OF  VAPORS. — All  va- 

lllustrate    the 

elasticity  of  pors  are  elastic,  like  air.  Steam,  like  air, 
vapors.  ft  compressed  in  a  cylinder,  with  a  close 

fitting  piston,  by  a  heavy  weight,  would  expand  again, 
and  force  the  piston  out,  as  soon  as  the  weight  were 
removed.  The  force  with  which  a  vapor  expands,  or 
strives  to  expand  supposing  the  weight  not  removed, 
is  called  its  elastic  force  or  tension. 


VAPOR.  67 

153.    DENSITY    DEPENDS  ON  TEMPERA- 

How  does  tern- 

perature  a/ect  TURE. — If  water  is  boiled  in  a  flask,  the 
density?  latter  Decomes  filled  with  steam>  But? 

although  full,  more  steam  can  be  crowded  into  the 
same  space.  On  corking  the  flask  and  continuing  the 
heat,  the  temperature  of  the  water  will  be  raised. 
Then,  forced  as  it  were,  by  the  additional  heat,  its  par- 
ticles have  the  power  of  crowding  into  the  steam  be- 
fore produced,  and  making  it  more  dense.  But  after 
a  time,  no  more  can  be  forced  in  until  the  temperature 
is  still  further  increased.  In  other  words,  there  is  a 
maximum  density  corresponding  to  every  temperature. 
And  what  is  here  said  of  steam,  is  true  of  vapor  of 
water  produced  at  lower  temperature,  and  also  of  other 
vapors.  The  higher  the  temperature,  the  greater  is 
the  density  of  all  vapors,  provided  a  surplus  of  material 
is  present.  But  if  this  is  not  the  case,  heat  has 
simply  the  effect  of  expanding  the  vapor  as  it  would 
an  equal  quantity  of  air.  In  the  case  of  a  partial 
supply  of  water,  the  vapor  grows  more  dense,  but 
does  not  reach  the  highest  density  which  it  would 
have  at  the  same  temperature  with  a  full  supply. 
TI™  ,  ,  154.  DISAPPEARANCE  OF  HEAT  IN  VA- 

What  remark- 
able   drcum-    TORS. — The   same   disappearance   of  heat 

stance  attends         ,   .    .  1-1-  j 

the  formation  which  occurs  when  a  solid  is  converted 
oj-  vapors?  ^Q  a  jjquj^  occurs  also  when  a  liquid  is 
converted  into  a  vapor  or  gas.  Thus,  if  we  wish  to 
cool  a  room  in  summer,  we  sprinkle  the  floor.  As  the 
water  evaporates,  much  of  the  heat  of  the  room  dis- 
appears. It  has  entered  into  combination  with  water 
to  produce  vapor,  and  has  no  longer  the  power  of  af- 


68  HEAT. 

fecting  the  senses  and  the  thermometer.  In  the  same 
manner,  our  bodies  are  cooled  in  summer  by  perspira- 
tion, and  the  evaporation  which  accompanies  it.  All 
vapors  may,  indeed,  be  regarded  as  combinations  of 
heat  with  the  liquids  from  which  they  are  formed. 
And  in  this  case,  also,  the  heat  which  becomes  latent 
in  thus  combining,  is  called  latent  heat. 

155.  FREEZING  BY  EVAPORATION. — The 

How  can  ether 

be  made  to  more  rapidly  a  substance  evaporates,  the 
^Explain*  ^its  niore  heat  does  it  require  for  the  evapora- 
action.  tioii.  This  it  obtains  from  objects  in  con- 

tact with  it.  Ether  may  be  made  to  evaporate  so 
rapidly  as  to  freeze  water,  even  in  summer.  This  is 
best  accomplished  by  covering  the  bottom  of  a  test- 
tube  with  a  cotton  rag,  or  several  layers  of  porous  f  p 
paper,  as  represented  in  the  figure,  dipping  it  into 
ether,  and  then  waving  it  to  and  fro  in  the 
air,  or  spinning  it  between  the  palms  of  the  hands. 
By  repeating  this  process  several  times,  a  few 
drops  of  water,  previously  placed  in  the  tube,  may 
be  frozen.  A  mixture  of  liquefied  carbonic  acid  and 
nitrous  oxide  gases,  previously  liquefied,  produce  on 
evaporation  a  temperature  of  220  degrees  below  zero. 
156.  PROTECTION  FROM  HEAT  BY  EVA- 

How  does  eva- 
poration pro-    PORATION. — By  previously  moistening  the 

tect  from  heat?     fingerS;  they  m&y  bu  dipped  unharmedj  for 

an  instant,  into  molten  lead,  or  passed  through  a  stream 
of  white-hot  iron  as  it  flows  from  the  furnace.  A 
cloak  of  comparatively  cool  vapor  is  formed  from  the 
moisture  upon  the  fingers,  and  keeps  them  from  con- 
tact with  the  molten  metal. 


VAPOR.  69 

pp> 

157.  RELATIONS  OF  AIR  AND  VAPOR. — 

•Does  vapor    rp^Q  earth   is  surrounded  by  air   to  the 

displace  air  ? 

depth  of  fifty  miles.  It  is  also  surrounded 
by  vapor  occupying  the  same  space  which  the  air  oc- 
cupies. But  they  are  independent  of  each  other. 
Each  contracts  for  itself,  and  expands  for  itself,  accord- 
ing to  the  temperature.  When  more  vapor  is  produced 
by  evaporation  from  the  sea,  or  other  sources,  it  rises 
into  the  air  without  displacing  it  or  pushing  it  aside, 
only  rendering  the  vapor  which  it  before  contained 
more  dense. 

158.  QUANTITY  OF  VAPOR  IN  THE  AT- 
^  vapor    M°SPHERE- — The  air  is  always  full  of  va- 
in the   por ;  that  is,  where  there  is  a  cubic  inch 

of  air,  there  is  a  cubic  inch  of  vapor  with 
it,  occupying  the  same  space. 

Upon        what  159'    QUANTITY    OF   WATER    THE  AIR  MAY 

does  the  quan-    CONTAIN  AS  VAPOR. — The  quantity  of  wa- 

tity   of  water  .        ,     *    .      . 

in  the  air  de-  ter  present  in  the  air,  in  the  form  of  trans- 
Pend?  parent  vapor,  depends  on  the  density  of  the 

vapor,  and  this  differs,  as  has  been  shown,  according  to 
heat  and  the  abundance  of  water.  In  summer,  and 
over  the  sea,  it  is  commonly  most  dense.  At  a  me- 
dium summer  temperature  of  75  degrees,  the  vapor  in 
the  air  is  sometimes  so  dense  that  every  cubic  yard  of 
air  contains  a  cubic  inch  of  water,  in  this  form.  But 
it  can  never  at  this  temperature  contain  more.  It  is 
then  said  to  be  "  saturated,"  and  also  that  its  capacity 
for  water  is  filled. 


70  HEAT. 

CAPACITY     OF     THE    AIR    FOR    WA- 


What       effect 

has  heat  upon     TER     INCREASED     BY     HEAT.  -  But,     as     the 

the  quantity  of 

vapor  present  weather  grows  warmer,  the  capacity  of 
the  air  for  moisture  is  increased,  so  that  at 
100°,  it  can  contain  twice  as  much  as  at  75°,  or 
two  cubic  inches.  On  the  other  hand,  as  the  weather 
grows  cooler,  its  capacity  is  diminished,  so  that  at  50° 
it  can  hold  scarcely  more  than  half  a  cubic  inch,  and  is 
saturated  by  this  comparatively  small  quantity.  And, 
in  general,  the  capacity  of  the  air  for  moisture  is  in- 
creased by  the  elevation  of  its  temperature. 

161.  EFFECT  OF  WIND.  —  Wind  causes 
evaporation  to  proceed  more  rapidly,  not 


tity  of  vapor   because  the  air  in  motion  has  any  greater 

in  the  air  ?  r  .   ,  •. 

capacity  for  moisture,  but  because  new 
portions  of  air  are  brought  successively  into  contact 
with  the  wet  surface.  As  fast  as  one  portion  has  im- 
bibed a  certain  amount  of  moisture,  another  portion  of 
drier  and  more  thirsty  air  takes  its  place. 

162.   DEPOSITION  OF  MOISTURE.  —  It  fol- 

Explain     the 

deposition  of  lows  that  air  that  is  saturated,  or,  in  other 
words,  has  its  full  portion  of  moisture  in 
the  form  of  vapor,  must  deposit  a  portion  of  it  in  the 
form  of  water  in  cooling.  Thus  a  cubic  yard  of  sat- 
urated air  at  75°,  on  being  cooled  down  to  50°,  would 
yield  half  a  cubic  inch  of  water,  or  half  of  the  whole 
quantity  which  it  originally  contained.  If  we  sup- 
pose the  experiment  to  be  performed  in  a  glass  vessel 
where  the  eifect  of  cooling  could  be  observed,  we 
should  first  see  a  mist  or  dew  within  the  box,  consist- 
ing of  the  particles  of  water  which  the  colder  air  can 


VAPOR.  71 

no  longer  retain.  This  mist  would  gradually  deposit 
and  collect  in  the  form  of  water,  and  if  measured, 
would  be  found  to  make  more  than  half  a  cubic  inch. 
Something  less  than  half  a  cubic  inch  would  remain 
as  invisible  vapor  in  the  cooled  air.  If  the  air  were 
cooled  further,  part  of  this  would  be  condensed  to 
water. 

What     is  163.  UNSATURATED  AIR.  —  Air  that  does 

said  of  unsat-    not  contain  its  complement  of  water  will 

urated  air  and 

its  moisture  ?  not  yield  any  by  slight  cooling.  It  would 
be  like  slightly  compressing  a  half-filled  sponge.  But 
as  the  cooling  proceeds,  the  vapor  becomes  so  dense 
that  further  cooling  will  cause  a  deposition  of  moisture. 
A  cubic  yard  of  air  at  75°,  containing  only  half  a  cubic 
inch  of  water  in  the  form  of  vapor,  would  yield  none 
on  being  cooled  down  to  50°.  At  this  point  the  formation 
would  commence.  If  it  contained  originally  less  than 
half  a  cubic  inch,  it  would  have  to  be  cooled  still  lower 
before  any  moisture  made  its  appearance.  The  less 
the  moisture,  in  short,  the  more  cold  it  would  require 
to  wring  it  out. 

Is  the  quantity  164.     QUANTITY    OF    VAPOR    IN    THE    AT- 

MOSPHERE—  As  has  been  already  stated, 


ways  propor-    the  capacity  of  air  for  vapor  is  in  propor- 

tioned    to   its       .  m,r      .        - 

warmth?  tion  to  its  warmth.  The  air  of  summer 
can  therefore  contain  more  than  that  of  winter  ;  and 
it  frequently  does  so.  But  this  is  not  necessarily  the 
case,  for  the  capacity  for  moisture  is  not  always  filled. 
Hot  air  over  a  desert,  for  example,  contains  less  mois- 
ture than  cold  air  over  the  sea.  And  in  the  same  lo- 
cality, and  during  the  same  season,  the  quantity  of 


72  HEAT. 

moisture  in  the  air  will  differ  from  day  to  day,  and 
from  hour  to  hour.  This  will  depend  a  good  deal  on 
the  wind,  whether  it  blows  from  the  land  or  from  the 
sea.  Sometimes  it  contains  a  cubic  inch  of  water  in 
the  form  of  vapor  in  every  square  yard,  but  generally 
less. 

165.  MIST    AND    FOG.  —  These    are 

What   is    the  1        . 

cause  of  mists  aqueous  vapor,  rendered  visible  by  the 
and  fogs?  cooling  of  the  air,  as  before  explained. 
When  the  air  is  saturated,  the  least  cooling  will  pro- 
duce a  fog,  as  in  the  case  supposed  in  paragraph  129. 
When  it  is  not  saturated,  more  cooling  will  be  required, 
as  in  the  case  supposed  in  the  subsequent  paragraph. 
The  beautiful  veil  of  mist,  which  forms  in  summer 
nights  over  low  places,  is  owing  to  the  cooling  of  the 
air  below  its  point  of  saturation,  which  takes  place 
after  sunset. 

166.  MIXED    CURRENTS  OF  AIR. — The 

££*»"  phenomena  of  mist>  f°g'  clouds> and  con- 

fogs  by  mixed   sequently  of   rain,    are    more    commonly 

currents  of  air  .  .  .  .,        ,  ,         , 

owing  to  the  mixture  of  cold  and  warm 
winds  or  currents  of  air.  When  this  admixture  takes 
place,  the  warm  air  becomes  colder,  and  tends  to  de- 
posit its  moisture,  and  the  cold  air  warmer  ;  and  it 
might  be  at  first  supposed  that  those  two  influences 
would  counteract  each  other.  For  example,  if  a  cubic 
yard  of  air  at  100°  mixes  with  a  cubic  yard  at  50°,  they 
both  become  75°,  and  it  might  be  thought,  that  the 
warming  of  the  colder  cubic  yard  would  increase  its 
capacity  for  moisture,  as  much  as  the  cooling  of  the 
warmer  cubic  yard  would  diminish  its  capacity,  and 


FOG.  73 

that  consequently  no  mist  would  be  produced.  But, 
as  before  stated,  it  has  been  ascertained  by  experiment 
that  hot  air  at  100°  will  contain  about  two  cubic  inches, 
and  air  at  50°,  about  half  a  cubic  inch  of  water.  The 
two  would  therefore  contain  two  and  a  half  cubic 
inches.  But  air  at  75°  can  hold  but  one  cubic  inch, 
and  consequently  the  two  cubic  yards  would  hold  but 
two  cubic  inches.  The  surplus  half  inch  would  con- 
sequently take  the  form  of  visible  moisture,  called 
cloud,  fog,  or  mist,  according  to  circumstances.  It  is 
not  to  be  understood,  from  what  is  above  stated,  that 
half  a  cubic  inch  of  water  is  always  yielded  by  every 
two  cubic  yards  of  air  at  50°  and  100°  which  come  to- 
gether ;  if  they  are  not  totally  saturated,  the  quantity 
will  be  less. 

167.  FOGS  ON   THE  SEA  COAST. — The 

Why  are  fogs 

produced  on  sea  is  cooler  than  the  land  in  summer,  and 
the  sea  coast?  warmer  m  winter.  As  a  consequence,  the 
air  above  the  sea  is  cooler  in  summer  and  warmer  in 
winter,  than  that  above  the  land.  The  admixture  of 
these  bodies  of  air,  which  takes  place  along  the  coast, 
produces  fogs  on  the  principle  above  stated. 

168.  FOGS  ON  RTVERS. — When  land  and 

Why   do  fogs 

form  on  riv-  water  have  the  same  temperature,  as  may 
be  the  case  with  small  lakes  and  rivers, 
the  difference  of  radiation  during  a  single  night  often 
produces  fogs.  The  land  cools  more  rapidly  than  the 
water.  As  a  consequence,  the  air  above  the  land  is 
cooler  than  that  above  the  water.  As  the  two  bodies 

of  air  mingle,  fog  is  produced,  and  is  seen  following 

4 


74  HEAT. 

the  devious  course  of  the  river,  or  brooding  over  the 
lake  in  the  morning. 

169.  NEWFOUNDLAND  FOGS.  —  The  fogs 

What     causes  __  ,,        , 

the  Newfound-  on  the  banks  of  Newfoundland  are  owing 
land  fogs?  ^Q  ^  mixture  of  cold  winds  from  the 
north,  with  the  warm  air  of  the  gulf  stream,  which 
passes  along  that  part  of  the  ocean. 

170.  CLOUD-CAPPED  MOUNTAINS.  —  The 
402?     °ro-    temperature  of  the  air  at  high  elevations 
duced  on  high    is  always  lower  than  at  the  general  level 

mountains? 

of  the  earth.  As  the  warm  breeze  comes 
up  from  the  warmer  valleys,  the  two  currents  min- 
gling, produce  clouds.  A  clear  atmosphere  through- 
out a  whole  day  is  rare,  on  high  mountains. 

171.  DEW  POINT.  —  It  has  been  already 


What  is  the    geen  ^^  ajr  ^as  to  be  cooled  more  or  less 

dew  point  ? 

before  it  yields  moisture,  according  to  the 
amount  which  it  contains.  If  it  contains  about  one 
cubic  inch  to  the  cubic  yard,  or,  in  other  words,  is  satu- 
rated, the  least  cooling  will  cause  the  appearance  of 
visible  moisture.  If  it  contains  half  as  much,  it  must 
be  cooled  down  to  50°  P.  If  it  contains  less  than  half 
as  much,  still  more  refrigeration  is  required.  The 
temperature  at  which  the  deposition  be- 
gins in  any  case  is  called  the  dew  point. 

172.     HOW    TO    FIND    THE 

How    can  the 

dew   point   be     DEW  POINT.  -  It  is  Common- 

ly  found  by  adding  ice,  lit- 
tle by  little,  to  a  glass  of  water  con- 
taining a  thermometer.  As  the  water 
grows  cool,  the  glass  cools  also,  and  as  a 


DEW.  75 

consequence,  the  exterior  air  immediately  in  contact 
with  it.  After  a  time,  moisture  begins  to  deposit.  The 
temperature  at  which  this  occurs  is  noted,  and  is  the 
dew  point. 

173.  DEW. — The    earth   cools,   as   has 

Explain     the  . 

formation  of  been  before  stated,  every  clear  night,  by 
radiation.  The  air  in  immediate  contact 
with  it,  becomes  thereby  so  much  cooler,  that  it  cannot 
retain  all  its  water  in  the  form  of  invisible  vapor,  and 
the  deposition  of  the  surplus  in  the  form  of  dew  is  the 
consequence. 

174.  Grass  and  foliage  receive  most  dew 
because  they  are  good  radiators,  and  losing 

the  most  their  own  heat  most  rapidly,  cool  down 
the  air  sufficiently  to  cause  a  deposition  of 
its  moisture.  The  soil  itself,  and  stones,  receive  less, 
or  none  at  all,  because  they  do  not,  by  their  own  ra- 
diation, become  sufficiently  cool  to  produce  the  same 
effect.  Dew  does  not  form  on  a  cloudy  night,  because 
the  clouds  radiate  heat  to  the  earth  and  thus  prevent 
the  requisite  cooling. 

175.    CAPACITY  FOR  VAPOR  :  EXPANSION 

How    is    it  -r.  .  -,  -i 

known  thatthe     NOT    THE  CAUSE. It  must  not  be  Supposed 

increased  ca-    that  the  increased  capacity  of  air  for  va- 

pacity   of  air  . 

for  moisture  por,  which  results  from  heating,  is  owing 
*°  to  its  exPansion.  Air  does  indeed  expand 
about  one-twentieth  between  50°  and  100°, 
but  its  capacity  for  moisture  is  quadrupled  by  the  same 
rise  of  temperature. 


76  HEAT. 

176.  ABSORPTION  NOT  THE  CAUSE. — It 
MM*  allorp-  is  not  uncommonly  supposed  that  the  air 
tion  is  not,  the  acts  to  absorb  vapor  as  a  sponge  does  to 
draw  up  water.  The  term  "  saturated" 
used  for  convenience  in  scientific  works  is  calculated 
to  give  this  impression.  But  vapor  rises  just  as  well, 
and  even  more  rapidly,  into  a  vacuum,  or  space  from 
which  all  the  air  has  been  removed. 

WJiat  then  is  177.    INCREASED    DENSITY  OF  VAPOR  THE 

the  cause?  CAUSE. — The  air  absorbs  any  vapor  that 
may  be  formed,  whether  more  or  less  dense.  At  higher 
temperatures,  denser  vapor  is  produced.  It  follows  that 
the  air  will  contain  more  water,  in  proportion  to  the 
elevation  of  its  temperature. 

178.  REMOVAL    OF    AIR  DOES  NOT  IN- 

Does  the  remo-  . 

val  of  air  in-     CREASE    THE    QUANTITY. It  might  be  SUD- 

"formation  *o/  Pose(^  tnat  more  water  would  rise  into  a 
vapor  ?  vacuum  in  the  form  of  vapor,  than  into  a 

space  filled  with  air,  on  the  ground  that  the  removal 
of  the  air  would  make  more  room  for  something  else. 
But  this  is  not  the  fact.  The  presence  or  absence  of 
air  makes  no  difference. 

179.  SEVERAL  GASES  AND  VAPORS  MAY 

Do  vapors  and  _     .,  1 ,  ,, 

gases    exclude     OCCUPY    THE   SAME  SPACE. It  follows  from 

each  other  ?  the  lagt  paragraph  that  vapors  do  not  dis- 
place the  air  ;  they  penetrate  it  instead.  And  it  is  a 
remarkable  fact,  that  a  number  of  vapors  may  occupy 
the  same  space  without  interfering  with  one  another  ; 
and  each  in  the  same  quantity  as  if  the  rest  were  ab- 
sent. 


VAPOR.  77 

Give  the  exam-  180.  Thus,  as  much  water  will  rise  in 
Ples-  vapor  into  a  jar  of  air  as  if  it  were  a  va- 

cuum. And,  in  addition  to  this,  as  much  alcohol  and 
ether  successively,  as  if  the  jar  were  entirely  empty. 
The  tension  or  pressure  from  within,  outward,  is,  of 
course,  increased  by  each  additional  vapor. 

181.    MOIST    AIR    LIGHTER    THAN    DRY. 

Why  is  moist 

air  lighter  It  would  naturally  be  supposed  that  air 
than  dry  air  ?  contajnjng  moisture,  would  be  heavier  than 
air  containing  none.  And  it  would  be  so,  but  for  the 
fact  that  the  presence  of  vapor  causes  the  air  to  ex- 
pand slightly,  and  grow  lighter,  and  this  to  an  extent 
more  than  sufficient  to  compensate  for  the  increase  of 
weight. 


BOILING. 

182.    WEIGHT  OF  THE  ATMOSPHERE. — 

lt        As  an  introduction  to  the  subject  of  boil- 


atmosphere       ing^  jt  will  be  necessary  to  consider  the 

has  weight  ?  - 

pressure  of  the  atmosphere.  The  earth  is 
surrounded  by  an  atmosphere,  estimated  to  be  fifty  miles 
high.  It  is  very  light  compared  with  the  earth  itself,  or 
with  water.  But  it  has  weight,  as  may  be  proved  by 
weighing  a  bottle  full  of  air,  and  then  pumping  out 
the  air  and  weighing  it  again.  The  empty  bottle  will 
be  found  to  weigh  less  than  the  bottle  full  of  air. 

183.   ANOTHER  PROOF   OF  THE  WEIGHT 

Give    another 

proof  that  air    OF  THE  AIR. — That  the  air  has  weight,  is 
has  weight.        again  proved  by  tying  a  piece  of  bladder 


78  HEAT. 

over  a  glass  cylinder,  open  at  both  ends,  placing  the 
open  end  air-tight  on  the  plate  of  an  air  pump,  and 
then  exhausting  the  air.  The  pressure  of  the  column 
of  air  that  stands  on  the  bladder  is  sufficient  to  break 
it,  and  the  air  settles  in,  as  effectually  as  if  it  were  a  col- 
umn of  iron.  The  atmosphere  exerts  such  pressure, 
amounting  to  about  fifteen  pounds  to  every  square  inch, 
on  all  parts  of  the  surface  of  the  earth. 

184.  A  SIMPLE  MEANS    OF  PROOF.  - 

Describe    a 

simple  means  Wind  a  stick  with  cotton  and  press 
°that°airl  *  has  it;  to  the  bottom  of  a  test-tube,  con- 
wight.  taining  enough  water  thoroughly  to 

moisten  it.  It  will  be  found  difficult  to  withdraw 
the  piston.  The  difficulty  arises  from  the  fact  that 
the  column  of  air  which  rests  upon  it,  must  be 
lifted  at  the  same  time.  Having  raised  it  a  little  way 
and  released  it,  the  piston  flies  with  force  to  the  bot- 
tom, owing  to  the  weight  of  the  same  column  of  air. 

185.  ELASTIC  FORCE  OF  THE  ATMOSPHERE. 
Every  cubic  inch  of  air  at  the  surface  of 


its  elastic  the  earth,  may  be  likened  to  a  piece  of  in- 
dia-rubber, which  has  been  compressed  into 
the  space  of  a  cubic  inch,  by  a  heavy  weight  placed  on 
it.  If  we  suppose  a  piece  of  rubber,  while  thus  com- 
pressed, to  be  confined  in  a  strong  metallic  box,  it  would 
evidently  exert  an  elastic  force  in  all  directions,  equal 
to  the  force  which  compressed  it.  So  the  lower  por- 
tions of  air,  which  are  kept  compressed  by  the  air 
above,  exert  elastic  force.  And  it  is  better  to  regard 
the  pressure  of  fifteen  pounds  on  every  square  inch  of 


PRESSURE    OF    THE    ATMOSPHERE.  79 

the  surface  of  the  earth,  as  a  consequence  of  the  elastic 
force  of  the  lower  portions  of  air,  rather  than  the  direct 
effect  of  the  weight  of  the  whole  air.  The  weight  of 
the  whole  atmosphere  produces  the  elastic  force  of  the 
lower  portions  by  compressing  them,  and  the  elastic 
force  of  the  lower  portions  exerts  the  pressure. 

Why  are  we  186.  WHY  THE  PRESSURE  OF  THE  AIR 
notcrushedby  DOES  NOT  CRUSH  US. If  a  thin  glaSS  V6S- 

the  pressure  of  '-  . -,      -,  -,  .    , 

the  atmo-  sel  were  turned  upside  down,  and  air-tight, 
sphere?  upon  a  table,  it  would  collapse  but  for  the 

fact  that  it  is  filled  with  air,  which,  according  to  the  last 
paragraph,  has  elastic  force  equal  to  that  of  the  air 
without.  So  our  bodies  would  collapse,  but  for  the  fact 
that  our  lungs,  and  all  of  the  cavities  of  the  body,  are 
filled  with  air,  possessing  the  same  elastic  force  as  the 
external  air  ;  a  force  which  it  had  acquired  by  compres- 
sion, before  it  was  taken  into  our  bodies. 

187.  QUANTITY  OF  WATER  THE  PRES- 

What  sustains 

the    water    in     SURE      OF     THE      AIR     WILL      SUSTAIN. If   a 

^uM^rfre-    tumD^er  be   filled  under  water,  and  then 

sentcd  in    the     lifted      OUt     bottom      Up- 

figure ?  1 

ward,  as  shown  in  the 
figure,  it  is  well  known  that  the  wa- 
ter will  not  run  out.  The  pressure 
of  the  atmosphere  on  the  surface  of 
the  water  outside,  keeps  the  water  forced  up  on  the  in- 
side. 

188.  The  effect  would  be  the  same  if 

What  quanti-      , 

tu  of    water   the  tumbler  were  twice  as  tall,  or  if  we 

•  *  i  *^  .  i 

suppose   it  lengthened  into  a  tube  thirty- 
three  feet   long.     If   a   still   longer   tube 


80  HEAT. 

were  used,  it  would  be  found  that  the  level 
of  the  water  inside,  would  never  be  more  than 
thirty- three  feet  above  the  level  outside.  The 
remainder  of  the  tube  wonld  be  empty,  as  re- 
presented in  the  figure.  In  other  words,  the 
pressure  of  the  atmosphere  will  sustain  a  col- 
umn of  water  thirty-three  feet  high.  Water 
rises  in  a  pump  from  this  cause. 

189.  QUANTITY  OF  MERCURY  THE 

incheTofnier-      PRESSURE   OF  THE   AIR    CAN  SUSTAIN. 

cury  will  the    in   performing    the    experiment  of 

air  sustain? 

the  last  paragraph  with  mercury,  it 
will  be  found  that  the  level  within  the  tube,  will 
be  thirty  inches  above  the  external  level.  In  other 
words,  the  pressure  of  the  atmosphere  will  sustain  a 
column  of  mercury  thirty  inches  high. 

190.  If  a  long  tube  is  used,  there  is,  of 

Explain  the  __  .      . 

Toricdlian  course,  an  empty  space  above.  This  is 
vacuum.  caiied  the  Toricellian  vacuum,  from  the 

fact  that  a  vacuum  was  first  produced  in  this  manner  by 
an  Italian  philosopher,  named  Toricelli.  It  is  not  an 
absolute  vacuum,  a  small  portion  of  mercury  being  al- 
ways present  in  the  space  in  the  form  of  transparent 
vapor. 

191.  BOILING. — Thus  far  we  have  con- 

Whatismeant       ••,-,,,,,,  .  /,  f 

by  the  term  sidered  solely  the  formation  of  vapors  from 
boiling?  the  surfaces  of  liquids<  But  where  any 

liquid  is  heated  up  to  a  certain  point,  vapor  forms  in 
bubbles  below  its  surface.  The  production  of  vapor 
with  ebullition  is  called  boiling. 


BOILING. 


81 


192.  Water  begins  to  boil  when  it  is 

What    is    the 

boiling  point  heated  up  to  212°  ;  alcohol,  at  173° ;  and 
OfWethcr '  ?  ether,  at  96°.  As  the  proper  temperature  is 
Of  alcohol  ?  first  reached  at  the  bottom  of  the  vessel, 
near  the  fire,  the  formation  of  bubbles  begins  there  ; 
and  as  the  surplus  heat  comes  in  below,  they  continue 
to  be  formed  at  this  point. 
Every  liquid  has  its  own  boil- 
ing point. 

How  much  193.      EXPAN- 

stcam  do  cubic  SION    m   BOILING. 

inches    of  wa- 
ter, alcohol,  A  cubic  inch   of 

and  ether   re-  ,      .,     -,     . 

spcctiveiy  pro-    water   boiled    in 
dnce?  an    Open   vessel, 

produces  1696  cubic  inches 
of  steam.  A  drop  one-tenth  of  an  inch  in  diameter, 
would  make  enough  to  fill  a  vessel  of  the  diameter 
of  one  and  a  fifth  inches.  A  cubic  inch  of  alcohol 
produces  about  500  cubic  inches  of  alcohol  vapor ;  one 
of  ether  about  250.  The  ether  vapor  is  most  dense, 
that  of  alcohol  next,  and  the  steam 
least  so. 

194.  DISAPPEARANCE  OF 

HEAT      IN      BOILING. If     a 

thermometer    be    held    in 

boiling  water,  it  indicates 
a  temperature  of  212°  F.  Continue 
the  fire,  and  although  heat  constantly 
passes  up  into  the  water  through  the 
bottom  of  the  vessel,  it  grows  no  hot- 
ter. The  steam  which  is  produced  has 
4* 


What  is  said 
of    the  disap- 
pearance of 
heat  in  boiling? 


82  HEAT. 

also  precisely  the  same  temperature.  Neither  water 
or  steam  are  hotter,  although  both  have  been  con- 
stantly taking  in  heat.  But  the  heat  has  not  been 
without  effect,  any  more  than  in  the  conversion  of  a 
solid  into  a  liquid.  It  has  combined  with  the  liquid 
to  form  the  steam.  In  this  case,  also,  the  heat  which 
disappears  is  called  latent  heat. 

195.  RELATION  OF  PRESSURE  TO  BOIL- 
Howdoespres-    ING. — In  order  that  a  bubble  of  steam  may 

sure  oppose         f  .       . 

boiling  ?  form,  it  is  necessary  that  a  small  portion 
of  water,  shall  expand  into  a  comparatively 
large  portion  of  steam  to  form  it.  But  the  atmosphere 
is  constantly  pressing  on  the  surface  of  the  water,  and 
acting  through  the  water,  in  all  parts  of  the  vessel,  to 
prevent  any  separation  of  particles  or  expansion.  The 
case  is  similar  to  that  of  a  piece  of  india-rubber  com- 
pressed beneath  a  mass  of  iron :  it  cannot  expand  ow- 
ing to  the  weight  of  the  iron. 

196.   HEAT  OVERCOMES  PRESSURE. — But 

Explain    how 

heat  overcomes  if  we  could  by  some  means  increase  the 
pressure.  elasticity  of  the  india-rubber,  it  would  ex- 
pand and  lift  the  iron.  So,  if  we  can  in  any  way  in- 
crease the  tendency  of  the  particles  of  water  to  sepa- 
rate, it  will  finally  be  strong  enough  to  overcome  the 
pressure  of  the  atmosphere  above  arid  affect  separation. 
Heat  has  this  effect.  As  the  water  becomes  hotter, 
the  tendency  of  its  particles  to  fly  apart  becomes 
greater  and  greater,  till,  at  last,  it  is  sufficient  to  over- 
come the  pressure  which  has  before  crowded  them  to- 
gether, and  a  bubble  of  steam  is  formed.  Others  im- 
mediately follow,  and  boiling  thus  commences.  This 


BOILING.  83 

takes  place  at  212°  Fahrenheit,  which  is  therefore  called 
the  boiling  point  of  water. 

197.  EFFECT   OF  HEIGHT  ON  BOILING. 

What  effect  .  ... 

has  height  on  At  great  elevations,  the  atmosphere  is,  m 
boiling?  factj  lighterj  and  there  is  iess  of  jt  above 

us,  and  the  consequence  is  that  water  boils  on  moun- 
tains, at  a  lower  temperature  than  in  the  valleys  below. 
It  is  found,  by  careful  observation,  that  an  elevation  of  five 
hundred  and  fifty  feet  above  the  level  of  the  sea,  makes 
the  difference  of  one  degree  in  the  boiling  point. 

198.  MEASUREMENT  OF  ALTITUDES.  — 
the    This  fact  once  established,  a  tea-kettle  and 


mountains  be    a   thermometer  are  the  only  requisites  for 

determined?  .         .      .    .  r  .  mi 

taking  the  height  of  a  mountain.  The 
summit  being  reached,  the  tea-kettle  is  boiled,  and 
the  heat  of  the  water  tested  by  the  thermometer. 
If  the  mercury  stands  at  211°,  it  is  known  that  the 
height  is  550  feet  ;  if  at  210°,  the  height  is  1100  feet  ; 
and  at  whatever  point  it  stands,  it  is  only  necessary  to 
multiply  550  by  the  number  of  degrees  depression  of 
the  mercury  below  212°,  to  ascertain  the  elevation.  On 
the  top  of  Mont  Blanc,  water  was  observed  by  Saus- 
sure  to  boil  at  184°.  This  gives  us  the  means  of  calcu- 
lating very  closely  the  height  of  that  mountain. 

199.   EFFECT  OF  DEPTH  ON  BOILING.  — 

What  effect 

kas  depth  on    In  mines    the  atmosphere  is  heavier,  and 
oihng?  there  is,  beside,  more  of  it  above  us,  than 

at  the  surface  of  the  earth.  Water  must,  in  consequence, 
be  more  highly  heated  before  it  will  boil.  550  feet 
makes,  as  before,  a  difference  of  one  degree.  We  are 
thus  provided  with  a  simple  means  of  determining  the 


84  HEAT. 

depth  of  mines.  Owing  to  various  causes,  the  atmo- 
sphere at  the  same  elevation  is  a  little  heavier  some 
days  than  others,  so  that  the  height  of  a  mountain  or 
the  depth  of  a  mine,  as  thus  measured,  would  not  be 
always  precisely  correct. 

200.     ARTIFICIAL    CHANGE   OF  BOILING 
POINT-  —  I*  is  obvious,  from  what  has  already 


of  liquids  be    been  stated,  that  all  it  is  necessary  to  do  to 

changed?  ,      ... 

change  the  boiling  point,  is  to  change  the 
pressure  of  the  atmosphere,  on  the  surface  of  the  water 
to  be  boiled.     To  produce  this  change  of  pressure,  it  is 
not  necessary  to  ascend  mountains,  or  to  descend  into 
mines  ;  it  may  be  done  by  removing  the  atmosphere 
by  artificial  means.     This  would  be  done  by  attaching 
a  tube,  air-tight,  to  the  mouth  of  a  test-tube  or 
flask  and  drawing  off  the  air  by  means  of  an  J^ 
air  pump.     Cold  water  may  thus  be  caused  to 
boil.     So  by  pumping  more  air  into  the  flask,  the 
pressure  would  be  increased,  and  the  boiling  point 
elevated  ;    and   by    this   means   boiling    water 
would  be  prevented  from  further  boiling.     This 
subject  is  further  considered  in  paragraph  204. 

201.  CULINARY  PARADOX.  —  Boil  some  wa- 

Descnbe     the  ,  .       . 

culinary  par-    ter  m  a  test-tube,  and  then  cork  it  tightly, 

while  steam  is  still  issuing  from  its 
mouth.  Though  removed  from  the  fire,  the  wa- 
ter will  still  continue  to  boil.  This  will  behest 
observed  by  inverting  the  tube,  as  the  bubbles  of 
steam  form  more  rapidly  from  the  cork  surface 
than  from  the  glass.  A  few  drops  of  cold  water 
sprinkled  on  the  tube  will  occasion  a  more  violent 


STEAM.  85 

ebullition  ;  while  on  the  other  hand,  boiling  water, 
or  the  application  of  flame,  will  cause  the  boiling  to 
cease. 

202.    EXPLANATION.—  The   principle  is 
e^        tne  same  as  m  tne  experiment  of  the  last 


the  culinary      paragraph.     As  the    steam   condenses,  by 

paradox.  r  .  .  .J 

the  cooling  influence  of  the  air,  a  partial 
vacuum  is  produced,  and  a  diminished  pressure,  which 
enables  the  water  to  boil  with  less  heat.  Cold  water, 
by  condensing  the  steam  and  removing  the  pressure 
more  perfectly,  increases  the  ebullition,  while  boiling 
water  or  flame  renews  the  steam,  and  consequent  pres- 
sure, and  therefore  checks  boiling. 

203.  WATER  HAMMER.  —  The   test-tube 
"  Water  Ham-    prepared  as  above,  is  a  simple  form  of  the 

"  water  hammer."  If  very  thoroughly 
cooled,  and  then  sjiaken  with  the  kind  of  motion  which 
would  be  required  to  make  a  bullet  rise  half  way  in 
the  tube  and  fall  again,  the  water  will  strike  like  lead 
on  the  bottom.  It  is  because  there  is  no  air  and  but 
little  vapor  present  to  break  its  fall. 

204.  SUGAR    BOILING.  —  When    syrup 

Now  may  sy-     .,.,,,  ,  ,. 

rup  be  boiled   is  boiled  down  under  the   ordinary  pres- 


z.  gure  Qf  tne  atmosphere,  it  is  apt  to  be 
browned  or  injured  in  flavor.  By  boiling  it  in  a  pan 
with  an  air-tight  lid,  and  pumping  off  the  air,  and  the 
vapor  as  fast  as  formed,  boiling  may  be  easily  effected 
at  a  temperature  as  low  as  150°.  This  method  is  put 
in  practice  by  sugar  boilers,  and  the  disadvantages  above 
mentioned  are  thus  avoided. 


86  HEAT. 

205.  In   cooking,   this  method   could 

Can  food    be 

cooked  by  the    not  be  employed.     The  water  might,  in- 

same  method  ?     ^^  be  made  tQ  boil  ftt  lgOOj  bm  the  boiling 

water,  owing  to  its  less  heat,  would  not  have  the  effect 
of  water  boiling  at  212°.  Many  vegetable  juices  and 
infusions  which  are  used  for  medicines,  and  would  be 
injured  by  a  high  temperature,  are  boiled  down,  like 
sugar  syrup,  under  diminished  pressure. 

206.  SlNQING      OF     THE    TEA-KETTLE. 

ringing  of  the  The  singing  sound  which  precedes  boiling , 
tea-kettle.  ^  owing  to  the  collapse  of  the  first  bubbles 
of  steam,  as  they  rise  into  the  colder  water  above. 
The  very  first  bubbles  that  form  are  not  steam,  but  air 
which  the  heat  expels.  Steam  bubbles  are  then  formed, 
which  rise  a  little  way,  and,  being  reconverted  into  water, 
contract,  and  finally  collapse.  If  the  heat  is  continued 
and  the  water  made  hotter,  the  next  are  able  to  rise 
further.  Finally,  when  the  water  becomes  as  hot  as 
the  bubbles,  they  make  their  way  through,  and  boiling 
is  thus  commenced. 

What  is  a  207.  STEAM  BOILERS. — The  boiler  is  the 

steam  boiler?  vessel  in  which  steam  is  formed.  From 
the  boiler  it  passes  to  other  parts  of  the  apparatus  to 
move  the  machinery.  Steam  boilers 
are  of  various  forms,  but  are  always 
made  of  great  strength,  to  resist  the 
internal  pressure  to  which  they  are 
subjected. 
Explain  the  208.  The  figure  repre- 

sents    an   or(jinary   steam    boiler,    with 


STEAM.  87 

the  pipe  which  conveys  the  steam  to  the  engine.  A 
safety-valve  is  also  represented,  which  will  be  more 
fully  explained  in  another  paragraph. 

209.  ELASTIC  FORCE  OF  STEAM.  —  Under 

How   great  is  . 

the  elastic  ordinary  circumstances,  the  elastic  force  of 
force  of  steam?  steam  is  obviously  equal  to  the  elastic  force 
or  pressure  of  the  atmosphere.  A  man  who  rises  from 
a  chair  with  a  fifty-six  pound  weight  on  his  shoulder, 
must  exert  an  extra  muscular  force,  equivalent  to  fifty- 
six  pounds,  in  rising  ;  and  he  must  continue  to  exert  it 
while  he  stands.  So  every  bubble  of  steam  must  have 
an  elastic  force  equal  to  that  of  the  air  which  it  lifts,  or 
it  cannot  be  formed  under  the  pressure  of  the  atmo- 
sphere, or  continue  to  exist  when  once  formed. 

210.  ELASTIC  FORCE,  HOW  INCREASED. 
As  lonS  as  the  vessel>  in  which  steam  is 


steam  'incrcas-  made,  is  open,  the  pressure  is  as  stated  in 
the  last  paragraph.  But  if  the  boiler  be 
closed  steam-tight,  and  the  heat  continued,  more  steam 
forms,  and,  crowding  into  the  same  space  above  the 
water  increases  the  pressure.  In  other  words,  the  space 
becomes  filled  with  denser  steam,  of  greater  elastic 
force  ;  and  the  force  is  finally  sufficient  to  burst  the 
boiler,  unless  it  can  find  some  vent. 

211.    INCREASED  TEMPERATURE  ACCOM- 

panies  in™™       PONIES     INCREASED     PRESSURE.  -  Steam    of 

creased   pres-    high  elastic  force  can  only  be  made  in  a 

sure  of  steam  ? 

close  vessel.  But  in  proportion  to  the 
increase  of  elastic  force,  is  the  increase  of  pressure  on 
the  surface  of  the  water.  Therefore,  the  boiling  point 
becomes  higher  and  higher,  or,  in  other  words,  the  wa- 


88 


HEAT. 


ter  has  to  grow  constantly  hotter,  in  order  that  steam 
may  form  ;  and  as  steam  always  has  the  temperature 
of  the  water  with  which  it  is  in  contact,  the  steam 
grows  constantly  hotter  also. 

212.   THE   EXACT  RELATION  OF  TEMPE- 

How    can  the 

exact  relations     RATURE    TO    PRESSURE. It     is    desirable    to 

iLr^STpre*-  know  tne  increase  of  pressure  for  each  ele- 
sure  be  deter-  vation  of  temperature.  A  steam  boiler  sup- 

mined?  ,.     .       .  .        _r 

plied  with  a  barometer  guage  and  a  thermo- 
meter affords  the  means  of  ascertaining  this  rela- 
tion. Or  it  may  be  done  by  a  very  small  boiler,  made  for 
the  purpose.  The  barometer  guage  is  nothing  more  than 
a  bent  tube  fitted  into  the  boiler,  open  to  the  air  at  the  top, 
and  containing  quicksilver  in  the  lower  part  of  the  bend. 
We  will  suppose  all  the  air  to  have 
been  expelled  from  the  boiler,  the  stop- 
cock through  which  it  made  its  escape 
closed,  and  the  whole  interior  to  be 
filled  with  steam.  As  more  steam  is 
produced,  pressure  is  increased,  and 
the  temperature  of  both  water  and  steam  rise,  as  before 
explained. 

What  pressure  213.  Where  the  temperature  has 
has  steam  at  reached  250°,  it  is  found  that  the  pres- 

2oO  .   at  <zti o  ? 

at  294  ?  How  sure  of  the  steam,  acting  through  the  water 
on  the  quicksilver,  is  sufficient  to  force  and 
hold  the  latter  thirty  inches  higher  in  one  arm  of 
the  tube  than  in  the  other.  But  the  steam  with  which 
the  globe  was  filled  when  the  stop-cock  was  turned,  ex- 
erted a  pressure  of  fifteen  pounds  per  square  inch,  just 
sufficient  to  balance  the  pressure  of  the  external  air,  and 


STEAM.  89 

prevent  its  forcing  the  quicksilver  before  it  and  crowding 
into  the  boiler  through  the  tube.  As  before  stated,  when 
the  thermometer  reaches  250°,  it  is  found  that  the  denser 
steam  will  not  only  balance  the  atmosphere,  but  has 
force  enough  to  lift  the  mercury  thirty  inches,  which  is 
equivalent  to  another  atmosphere.  Steam  at  250°,  and 
in  contact  with  water,  is  therefore  said  to  exert  a  pres- 
sure of  two  atmospheres,  or  thirty  pounds  to  the  square 
inch.  At  275°  it  has  a  pressure  of  three  atmospheres  j 
and  at  294°,  of  four. 

What   is  said  214.      ALL    VAPOR     HAS    ELASTIC    FORCE. 

%rcfofvaStors  The  aPParatlls  Just  described  shows  the 
at  low  tem-  pressure  of  steam  at  and  above  212  degrees. 
per  But  vapor  of  water  has  elastic  force  at  all 

temperatures.  This  is  best  shown  by  passing  a  little 
water  up  into  a  Toricellian  vacuum,  and  observing  the 
effect.  The  water  is  introduced  by  blowing  it 
through  a  glass  tube,  one  end  of  which  is  brought 
under  the  mouth  of  the  inverted  tube.  The 
drop  rises  and  floats  on  the  mercury,  and  as 
vapor  forms  at  all  temperatures,  a  portion  of 
it  is  immediately  converted  into  vapor.  At 
the  same  time  the  level  of  the  mercury  is  de- 
pressed. It  is  crowded  down  in  opposition  to 
the  pressure  of  the  air  outside,  by  the  elastic 
force  of  the  vapor  formed.  For  the  sake  of 
simplicity,  the  space  above  the  mercury  was 
supposed  to  be  a  vacuum,  but  the  effect  is  the 
same  as  if  it  is  filled  with  air.  For,  as  has 
been  already  shown,  vapor  is  produced  as  well  in 
air  as  a  vacuum,  and  with  the  same  elastic  force.  If 
the  top  of  the  tube  is  warmed,  denser  vapor  is  formed 


90  HEAT. 

possessing  greater  elastic  force,  and  the  mercury  sinks 
lower,  till  at  212°    the    elastic  force  within,  is  equi- 
valent to  the  pressure  of  the  atmosphere  without,  and 
the  mercury  is  pressed  down  to  the  external  level. 
Explain  the  215.    BAROMETER-GUAGE. — The   princi- 

construction      ^tle  of   the    barometer-guage  has   already 

and  use  of  .  & 

the  barometer-  been  explained.  A  few  words  will  be 
guage.  added  here  as  to  its  use  and  construc- 

tion. It  is  always  desirable  to  know  the  pressure 
in  a  steam  boiler,  as  an  evidence  of  safety,  and  in 
order  that  the  fires  may  be  regulated  accordingly, 
and  no  more  fuel  be  consumed  than  is  necessary. 
Sometimes  the  tube  containing  the  quicksilver  is  of 
glass,  and  then  the  height  of  the  mercury  can  be  seen. 
In  other  cases  it  is  made  of  iron,  and  the  change  of 
level  of  the  quicksilver  is  indicated  by  a  float. 

216.    OTHER  STEAM    GUAGES. — A    ther- 

Explain  the 

thermometer-  mometer  may  be  made  to  answer,  perfectly, 
guage.  ^Q  purpose  of  a  steam  guage,  as  is  evi- 

dent from  what  has  been  said  in  paragraph  213.     The 
advantage  of  such  a  guage  is,  that  it  takes  but  little 
room  ;  its  disadvantage,  that  it  is  liable  to  be  broken. 
217.  There  is  still  another  kind  of  guage, 

Explain  the         . 

prfndpie  of  m  which  the  force  of  the  steam  operates 
another  guage.  on  a  metallic  spring,  which  moves  an  index 
more  or  less,  according  to  the  pressure.  The  spring 
guage  is  commonly  used  in  locomotive  boilers. 

Explain  the  ^18.     ACTUAL     PRESSURE    IN    DIFFERENT 

di/erence  be-     ENGINES. — The  actual  pressure  of  steam, 

twefn  high  and  . 

low  pressure      used  in  different  forms  of  the  steam  en- 
gine,  varies  very  widely.     There  are  low 


THE    STEAM    ENGINE.  91 

and  high  pressure  engines.  In  the  former,  steam  of 
ten  to  thirty  pounds  effective  pressure  is  used  ;  in  the 
latter,  the  pressure  often  reaches,  and  sometimes  ex- 
ceeds, seventy-five  pounds.  To  measure  the  pressure, 
the  steam  guage  described  in  paragraph  215  would  have 
to  be  five  or  six  feet  long.  It  is  on  account  of  this  in- 
convenient length,  that  other  guages  are  often  substi- 
tuted. 

Whatismeant  219'  EV  effective  pressure,  is  meant  the 
by  e/ective  surplus  over  and  above  that  which  is  neces- 
pre  sary  to  counterbalance  the  pressure  of  the 

atmosphere,  or  that  of  the  uncondensed  steam,  on  the 
opposite  side  of  the  piston. 
„    ,  .        ,         220.   SAFETY-VALVE. — The  safety-valve 

Hixplam  ana 

illustrate  the  is  a  contrivance,  by  means  of  which  the 
PthTsafetij  steam  finds  vent  through  a  hole  in  the 
valve.  boiler,  whenever  its  force  becomes  too  great 

for  safety.  A  piece  of  metal  shaped 
somewhat  like  a  decanter  stopper,  fits 
into  the  hole  above  mentioned,  and  is 
loaded  by  a  weight,  which  can  be  made  , 
greater  or  less  at  pleasure.  As  long  as  the  steam  has 
not  too  great  pressure,  the  stopper  continues  in  its 
place,  and  the  boiler  is  as  tight  as  if  it  had  no  such 
opening.  When  this  pressure  is  exceeded,  the  valve  is 
lifted,  and  stearn  escapes.  The  stopper,  being  loaded, 
falls  back  again,  as  soon  as  the  pressure  is  relieved. 

221.   THE  STEAM  ENGINE. — The  power 

Explain  the  . .     ,   .  . 

principle  of       applied  in  the  steam  engine  is  the  elastic 

ttetteamen-    force  of  steam.     The   figure    represents  a 

cylinder  and  close  fitting  piston,  and  tubes 


92  HEAT. 

through  which  steam  maybe  admitted  at  pleasure,  either 
above  or  below.  When  the  valve  in  the 
lower  tube  is  opened,  the  steam  under  pres- 
sure  in  the  boiler,  expands  and  enters  the  cyl- 
inder, lifting  the  piston.  If  the  steam  is  next 
admitted  above,  it  drives  the  piston  back 
again,  and  the  latter  may  thus  be  kept  in  con- 
stant motion,  and  made  to  move  wheels, 
shafts,  or  other  machinery.  It  is  only  necessary,  that 
whenever  steam  enters,  that  which  is  on  the  other  side 
of  the  piston  shall  find  its  way  out,  into  the  air.  Valves 
are  provided  for  this  purpose,  which  are  opened  and 
closed,  at  the  right  time,  by  the  machinery  which  the 
piston  itself  moves. 

222.   HIGH  PRESSURE  ENGINE. — The  en- 

Whatisahigh 

pressure  en-  gine,  here  described,  is  called  the  high  pres- 
sure engine.  The  steam  which  moves  it, 
must  evidently  have  elastic  force  greater  than  that  of 
the  atmosphere,  or  it  cannot  expand  and  drive  out  the 
waste  steam,  in  opposition  to  the  elastic  force  of  the 
air.  Steam  of  much  higher  pressure  is  used  in  such 
engines,  than  in  those  to  be  next  described,  and  hence 
their  name. 

223.  Low  PRESSURE  ENGINE. — The 
same  fiSure  wil1  answer  to  illustrate  the 
\ow  pressure  engine.  The  difference  is, 

sure  engne.  ,  .,     . 

that  the  steam  which  has  been  used  is 
not  driven  out.  but  disposed  of,  on  the  spot,  by  con- 
verting it  into  water.  The  advantage  of  this  will 
be  readily  perceived.  Suppose  the  space  above  the 
piston  to  be  full  of  steam.  A  jet  of  water  is  made  to 


THE    STEAM    ENGINE.  93 

play  into  it  and  condense  the  steam,  and  thereby  pro- 
duce a  vacuum.  When,  immediately  afterward,  steam 
is  admitted  below  the  piston,  the  latter  has  nothing  on 
the  other  side  to  drive  out,  and  consequently  rises  more 
easily.  As  less  force  is  required,  steam  of  lower  pres- 
sure may  be  used,  with  a  corresponding  economy  of 
heat  and  the  fuel  required  in  its  producton. 

224.  THE  CONDENSER. — In  steam  en- 
we'and' Object  ginesj  as  now  made,  the  water  used  to  con- 
ey the  con-  dense  the  steam,  does  not  come  into  the 

cylinder  itself,  but  into  a  side  vessel,  called 
the  condenser.  The  steam  expands  into  this  vessel,  and 
is  condensed,  producing  a  vacuum  in  the  cylinder 
itself,  as  effectually  as  if  the  water  were  there  intro- 
duced. The  object  of  the  modification  is  to  avoid 
cooling  the  cylinder,  and  thereby  diminish  the  ef- 
fect of  the  steam  subsequently  entering  from  the 
boiler.  This  engine  is  called  the  low  pressure  engine, 
from  the  fact  that  steam  of  lower  pressure  may  be  em- 
ployed to  move  it  than  is  the  case  with  the  engine  pre- 
viously described.  It  may,  indeed,  be  made  to  run 
with  vapor  formed  below  212°,  instead  of  steam.  But 
in  practice,  steam  of  from  ten  to  thirty  pounds  effective 
pressure  is  employed. 

225.  ORIGINAL  STEAM  ENGINE. — In  the 
original  low  original  form  of  the  steam  engine,  the  pres- 
presmrecn-  sure  of  the  atmosphere,  instead  of  steam, 

was  applied  on  one  side  of  the  piston,  and 
it  therefore  received  the  name  of  the  atmospheric  engine. 
Suppose  the  cylinder  in  the  last  figure  to  be  open  at 
the  top,  and  the  piston  at  its  full  height.  On  condens- 


94  HEAT. 

ing  the  steam  below  it,  the  piston  would  evidently  sink, 
in  consequence  of  the  pressure  of  the  atmosphere.  By 
thus  employing  steam  pressure  on  one  side,  and  atmo- 
spheric pressure  on  the  other,  a  constant  motion  would 
be  realized.  But  the  effective  power  would  evidently 
be  less  than  in  the  low  pressure  engine,  because  part 
it  would  have  to  be  expended  each  time  in  lifting 
the  piston,  in  opposition  to  the  pressure  of  the  atmo- 
sphere. 

226.  A  test-tube  provided  with  a  pis- 

Tfrrtlfiin  the 

.  f  ton  made  of  cork,  or  better  of  w^ood  w^ound 

figure. 

with  cotton,  suffices  perfectly  to  illus- 
trate the  source  of  power  in  the  steam  engine.  On 
boiling  a  little  water  in  the  tube,  the 
piston  rises.  On  dipping  it  into  cool 
water,  and  thus  condensing  the  steam, 
the  piston  is  forced  down  to  the  bot- 
tom, as  in  the  original  form  of  the 
low  pressure  engine.  In  the  ascent 
of  the  piston,  the  analogy  is  not 
perfect ;  for  it  is,  in  this  case,  the 
production  of  new  steam,  and  not,  as  in  the  steam  en- 
gine, the  expansion  of  steam  already  produced,  that 
causes  the  piston  to  ascend. 

227.  STEAM  USED  EXPANSIVELY. — It  is 

Explain  the 

action  of  steam  not  necessary  in  the  steam  engine,  that 
steam  be  made  to  flow  from  the  boiler  du- 
ring the  whole  movement  of  the  piston, 
from  one  end  of  the  cylinder  to  the  other.  When  the 
cylinder  is  partly  filled,  the  supply  is  cut  off,  and  the 
steam  already  introduced  forces  the  piston  through  the 


STEAM.  95 

remainder  of  the  distance,  by  its  own  expansive  force. 
By  this  arrangement,  instead  of  using  a  cylinder  full 
of  steam  at  each  movement  of  the  piston,  only  one- 
fourth,  or  even  less,  according  to  its  density,  suf- 
fices. Steam  employed  in  this  manner  is  said  to  be 
used  expansively.  The  term  is  applied  especially  to 
this  case,  although  it  is  a  fact  that  steam  always  acts 
expansively. 

228.  CONVERSION  OF  VAPORS    INTO  LI- 
pors  convened    QUIDS.— If  a  vapor,  in  any  way,  loses  its 
into  liquids?     latent  heat,  it  at  once  becomes  liquid.     If, 

for  example,  steam  be  led  into  a  cool  pipe, 
the  metal  abstracts  the  latent  heat,  and  the  steam  be- 
comes water.  At  the  same  time,  the  heated  pipe  im- 
parts warmth  to  the  air  around  it. 

229.  HEATING    HOUSES    BY    STEAM.— 

How  are 

houses  heated  Houses  are  thus  heated,  by  steam  pipes 
passing  through  the  various  apartments. 
The  pipes  abstract  the  heat,  and  give  it  out  again  to  the 
air  of  the  house.  The  steam  thus  converted  into  wa- 
ter, runs  back  into  the  boiler  to  be  reheated,  and  to  start 
again  on  its  journey.  And  as  long  as  heat  is  supplied, 
the  water  continues  its  service  as  a  carrier  of  heat. 

230.  WATER  HEATED  BY  STEAM. — When 

How  is  water 

heated  by  steam  is  led  into  water,  the  effect  is  the 
same  as  on  leading  it  into  a  cold  pipe. 
The  water  abstracts  its  latent  heat,  and  becomes  hot, 
while  the  steam  itself  becomes  additional  hot  water. 
Water  in  different  parts  of  a  room,  or  even  of  a  large 
manufacturing  establishment,  may  thus  be  made  to 


96 


HEAT. 


boil  by  one  fire  ;  steam  being  led  into  it,  by  long  pipes, 
from  a  single  boiler. 

Prove  that  231.       PROOF    THAT    BOILING    IS    EFFECT- 

boihng  tsef-      ED  BY  LATENT  HEAT.—  No  amount  of  boiling 

fected   by   la- 

etnt  heat.  water,  if  poured  into  cold  water,  will  make 
it  boil.  But  steam  no  hotter  than  the  boiling  water,  if 
led  into  cold  water,  will  have  this  effect.  Now,  as  both 
the  hot  water  and  the  steam  were  the  same  in  respect  to 
sensible  heat,  if  the  steam  effects  what  the  water  does 
not,  it  is  evident  that  it  must  do  it  by  hidden,  or  latent 
heat.  It  is  only  latent  heat  which  the  steam  loses,  for 
it  becomes  itself  converted  into  equally  hot  water. 

232.  QUANTITY      OF      LATENT    HEAT.  -  A 

How  much  la-        . 

tent  heat  does    pint  of  water   will  make    enough    steam 

steam  contain?     t()  fiu  ft  globe  ^^  f()ur  feet  m  diameter< 

If  this  amount  of  steam  could  suddenly  become  a  pint 
of  water,  and  be  prevented  from  flying  off  into  steam 
again,  it  would  become  red  hot.  The  latent  heat  of  the 
steam  would  have  raised  the  temperature  from  212°  to 
1212°  —  a  thousand  degrees.  Steam  is  therefore  said  to 
contain  1000  degrees  of  latent  heat.  Vide  App. 

233.  SUM     OF      SENSIBLE      AND      LATENT 

HEAT    ALWAYS    THE    SAME-  —  Vapor  formed 


sensible  to  la-    by  the  heat  of  summer,  occupies  more  space, 

tent  heat?  7,  ,. 

and  contains  more  heat,  in  a  latent  condi- 
tion, than  is  contained  in  steam.  And  it  is  found  to  be 
a  universal  fact  that,  just  in  proportion  as  vapor  or 
steam  feels  cool,  or  indicates  a  lower  temperature  to 
the  thermometer,  it  contains  more  latent  heat  to  the 
same  quantity  of  water.  The  sum  of  the  sensible  and 
latent  heat  is  always  the  same  -about  1200°  degrees. 


DISTILLATION.  97 

Why   is  there  ECONOMY    IN   EVAPORATION. It  fol- 

no  economy  in    lows  that  evaporation  at  low  temperatures. 

evaporating  at  . 

low  tempera-  such  as  is  practiced  sometimes  in  sugar- 
houses,  has  no  advantage  of  economy. 
The  vapor  that  passes  off,  carries  with  it  less  sensible 
heat,  but  enough  more  latent  heat  in  proportion,  to  make 
up  the  difference. 

235.     DISTILLATION. — Distillation  con- 

Descnoe      the 

process  <>/  dis-  sists  in  converting  a  liquid  into  vapor,  and 
recondensing  the  vapor.  The  apparatus 
represented  in  the  figure, 
suffices  for  illustration. 
Water  being  boiled  in  the 
test-tube,  the  steam  con- 
denses in  the  cooler  vial. 
If  the  latter  be  covered 
with  wet  paper,  the  con-  "~ 
densation  is  more  perfect.  The  apparatus  commonly 
used  in  distillation,  consisting  of  retort  and  receiver,  is 
represented  in  the  appendix. 

236.  OBJECT  OF  DISTILLATION. — The  ob- 
object*}  *&%>  Ject  °f  distillation  is  commonly  to  purify, 
tiilationf  Or,  in  other  words,  to  separate  the  liquid 
distilled,  from  other  substances  with  which 
it  may  be  mixed.  Thus,  sea  water  is  distilled  to  sepa- 
rate the  pure  water  from  salt.  The  water  becomes 
steam,  and  is  condensed  as  pure  water,  while  the  salt 
remains  behind.  So  alcohol  is  distilled,  or  converted 
into  vapor,  and  recondensed,  to  separate  it  from  water, 
and  the  various  refuse  matters  which  are  mixed  with 
it  after  fermentation.  But  the  separation  is  not  per- 

5 


HEAT. 


feet,  for,  althougn  alcohol  is  more  volatile,  and  distils 
more  rapidly,  a  portion  of  water  always  distils  with  it. 
Distilled  liquors,  therefore,  always  contain  a  certain 
proportion  of  water. 


MAGNETISM.  99 

CHAPTER  IV. 

ELECTRICITY  AND  MAGXETISM. 
237.  NATIVE  MAGNETS. — The  native  mag- 

What  proper- 
ties has  the  na-    net,  or  loadstone,  is  a  mineral  which  has 

tive magnet?  the  remarjcable  property  of  attracting  me- 
tallic iron  to  itself,  and  of  taking  north  and  south  di- 
rection, when  suspended  and  free  to  move.  Particles 
of  iron  brought  near,  rush  toward  it,  and  remain  at- 
tached to  its  surface,  without  any  visible  cause.  It  ex- 
erts this  attractive  force  just  as  well  through  wood, 
stone,  or  any  other  material,  as  through  the  air. 

23$.    ARTIFICIAL    MAGNET. — The  same 

Describe  an  .  1-1  • 

artificial  mag-  properties  may  be  imparted  to  a  piece  of 
steel,  by  a  process  to  be  hereafter  described. 
Such  a  piece  of  steel  thereby  becomes  itself 
a  magnet.  Magnets  are  often  made  of  a  shape 
approaching  that  of  a  horse-shoe,  the  two 
poles  being  brought  near  to  each  other.  A 
piece  of  soft  iron,  called  an  armature,  is  placed  across 
the  end  to  prevent  the  loss  of  magnetic  power,  which  is 
found  otherwise  to  occur. 

239.  MAGNETIC  NEEDLE. — If  a  steel  bar 

What  is  the 

magnetic  nee-  be  made  into  a  magnet,  and  then  balanced 
on  a  pivot,  it  will  turn,  until  one  end  points 
north  and  the  other  south.  That  which  ^ 
moves  toward  the  north  is  called  the  north 
pole,  and  the  other  end  the  south  pole. 
A  small  bar  thus  balanced  is  called  a  mag- 


too 


MAGNETISM. 


netic  needle,  and  is  the  essential  part  of  the  mariner's 
compass. 

240.  ATTRACTION  OF  MAGNETS  FOR  EACH 

How  do  the  . 

poles  of  mag-  OTHER. — The  law  of  attraction  between 
'each^tter?  magnets  is,  that  unlike  poles  attract,  and 
like  poles  repel.  The  north  pole  of  one 
magnet,  therefore,  attracts,  and  is  attracted  by  the  south 
pole  of  another. 

241.  WHY  THE  MAGNETIC  NEEDLE  POINTS 
In^gneriT  nee-    N°RTH. — In  accordance  with  the  law  stated 
die  point          in  the  last  paragraph,  the  tendency  of  the 

noTth  ? 

magnetic  needle  to  point  north,  may  be  ac- 
counted for  by  supposing  the  south  pole  of  an  enor- 
mous magnet,  to  exist  somewhere  near  the  north  pole 
of  the  earth.  If  we  call  the  end  of  the  needle  which 
points  north  its  north  pole,  it  is  evident  that  the  sup- 
posed pole  at  the  north  must  be  a  south  pole.  For  the 
same  reason,  xve  might  suppose  the  north  pole  of  an 
enormous  magnet  to  exist  near  the  south  pole  of  the 
earth.  Connecting  these  poles,  we  should  accordingly 
have  an  immense  magnet  running  through  the  earth 
from  north  to  south.  This  supposition  will  account 
for  many  of  the  phenomena  of  magnetism ;  but  it  is 
not  supposed  to  be  the  true  one.  Another  theory  is 
presented  in  a  subsequent  paragraph. 

242.     INDUCED     MAGNETISM. — When    a 

Sio;To/~       Piece  °f  *ron  is  brought  near  to  a  magnet, 
magnetism,  in   the  iron  receives  magnetism,  by  induction, 

soft  iron.  .,  .  . .,  ., 

and  becomes  itself,  temporarily,  a  magnet. 
If  approached  to  the  south  pole,  its  adjacent  end  ac- 


MAGNETISM.  101 

quires  north,  and  the  remote  one  south  polarity,  and 
mutual  attraction  results.  By  virtue  of  its  ac- 
quired or  induced  magnetism,  it  will  attract  an- 
other piece  of  iron,  as  is  represented  in  the  figure, 
and  affect  it  in  all  respects  similarly.  From  the 
second  key,  another  smaller  one  may  be  sus- 
pended, and  from  this  another,  and  so  on.  It  is 
only  necessary,  that  each  successive  object  shall  be 
smaller  than  the  one  to  which  it  is  attached.  The 
magnetism  thus  acquired  is  only  temporary  in  the  case 
of  iron,  but  in  the  case  of  steel  it  is,  in  some  degree 
permanent,  and  may,  by  the  proper  means,  be  rendered 
entirely  so. 

243.    DIAMAGNETISM. — If   a  needle  of 
What  is  said     jron  be  hung,  by  a  thread,  between  the 

of  diamagnet-  J 

ism?  poles  of  a  horse-shoe  magnet,  it  immedi- 

ately turns,  so  that  one  of  its  ends  points 
to  the  north  pole,  and  the  other  to  the  south.  This 
is  also  a  consequence  of  induced  magnetism,  as  ex- 
plained in  the  preceding  paragraph.  The  metal  nickel, 
oxygen  gas,  and  many  other  substances,  both  solid, 
liquid,  and  gaseous,  are  similarly  attracted  by  the 
poles  of  a  magnet,  though  in  a  much  less  degree.  All 
bodies  which  are  not  attracted  are  repelled,  and  if  sus- 
pended between  the  poles,  turn  so  as  to  bring  their  ex- 
tremities as  far  away  from  the  poles  as  is  possible. 
The  former  class  are  called  magnetic,  and  the  latter 
diamagnetic  bodies.  To  show  the  phenomena  of  at- 
traction and  repulsion  with  gases  and  liquids,  the  mate- 
rials are  inclosed  in  tubes  or  bulbs.  In  the  case  of  most 
substances,  excepting  iron,  these  effects  can  only  be  at- 


102  ELECTRICITY. 

tained  by  means  of  powerful  magnets  and  delicate  ap- 
paratus. 

ELECTRICITY. 

244.     FRICTIONAL    ELECTRICITY. — If  a 

tional  dectri-  glass  tube  be  rubbed  with  silk,  it  will  after- 
city?  ward  attract  to  itself  filaments  of  the  silk, 

as  a  magnet  attracts  iron.  Or,  if  the  knuckle  be  ap- 
proached to  the  tube,  a  spark  may  be  drawn  from  it. 
These  phenomena  are  called  electrical.  Both  glass  and 
silk  are  said  to  be  electrically  excited.  The  same  ex- 
periment may  be  made  with  a  stick  of  sealing-wax. 

State  the  theory          245.    THEORY  OF  ELECTRICITY. AcCOrd- 

of  electricity.  jDg  to  fae  vjew  COmmonly  entertained  of 
these  phenomena,  both  glass  and  silk  contain  two  electri- 
cal fluids  in  a  state  of  combination,  which  are  so  sepa- 
rated by  friction,  that  the  positive  fluid  of  both  ac- 
cumulates in  the  glass,  and  the  negative  in  the  silk. 
The  positive  sustains  the  same  relation  to  the  negative, 
that  the  north  polarity  of  a  magnet  does  to  the  south  ; 
and,  in  consequence  of  the  difference  of  the  separated 
fluids,  the  two  bodies  containing  them  attract  like  op- 
posite poles  of  a  magnet.  It  is  also  true,  that  similarly 
electrified  bodies  repel  like  similar  poles  of  magnets. 
As  in  the  case  of  heat  and  light,  we  know  nothing  of 
the  electrical  fluid,  save  by  its  effects. 
Illustrate  by  ^46.  The  human  body  may  also  be  elec- 
examples.  tricially  excited,  so  as  to  yield  a  spark,  by 
rapid  sliding  over  a  carpet.  Gas  may  be  lighted  by  the 
spark.  The  gas  in  certain  manufactories  is  instantane- 


GALVANIC    ELECTRICITY.  103 

ously  lighted  throughout  the  whole  establishment  by 
electricity  developed  by  the  friction  of  the  machinery. 

247.  CONDUCTION  OF  ELECTRICITY. — Like 

Explain  the  .    . 

conduction  of     heat  or  caloric,  electricity  may  be  conducted 

electricity.  ^Qm  Qne  body  tQ  another<      ThuSj  if  ft  piece 

of  metal  be  electrically  excited,  or,  in  other  words, 
charged  with  a  quantity  of  either  the  positive  or  nega- 
tive fluid,  another  piece  of  metal  will  immediately  be- 
come so  on  connecting  it  with  the  first  by  a  metallic 
wire.  The  connection  being  formed,  it  will  attract  or 
repel  filaments  of  silk  or  other  material,  precisely  as  the 
first  one  does.  The  fluid  is  supposed  to  flow  from  one 
piece  of  metal  to  the  other,  through  the  wire,  and  we 
therefore  speak  of  a  current  of  electricity.  But  it  is 
not  certain  that  any  thing  actually  passes,  any  more 
than  in  the  case  of  light  and  heat  before  considered; 

248.  GALVANIC  ELECTRICITY. — It  is  also 

What  is  gal- 
vanic electri-     found   that  electricity  is  developed  when 

Clty  ?  two  metals  are  placed  in  contact  with  each 

other,  and  with  an  acid  at  the  same  time,         <    «« 
as  is  represented  in  the  figure.     This  is 
called  galvanic  electricity,  from  the  name 
of  an  early  experimenter  in  the  science. 
The  acid  acts  on  the  zinc,  arid  the  cur- 
rent flows  continuously  in  the  direction 
indicated  by  the  arrows.     This  apparatus  is  the  sim- 
plest form  of  the  galvanic  battery. 
,„,  .  .  249.  ELECTRODES. — For  convenience  in 

What  is  an 

electrode  ?  certain  experiments,  it  is  customary  to  at- 
tach platinum  wires,  to  the  exterior  portions  of  the  me- 
tallic slips.  These  are  called  electrodes.  The  wire  con- 


104  GALVANIC    ELECTRICITY. 

nected  with  the  copper  forms  the  positive  electrode,  and 
the  one  attached  to  the  zinc,  the  negative. 

250.  Platinum  wire  is  chosen,  because 

Why  is  plati- 
num used  for    there  is  frequent  occasion  to   immerse  the 

electrodes  ?  electrodes  in  corrosive  liquids,  and  this  me- 
tal, for  the  most  part,  withstands  their  action.  For 
many  experiments,  it  is  found  best  to  flatten  the  ends 
of  the  wires  forming  the  electrodes,  so  as  to  produce 
a  larger  surface.  The  same  object  may  also  be  effected 
by  terminating  them  with  strips  of  platinum. 

251.  ELECTRICAL  CONDITION  OF  ATOMS. 

What  is  the  ,,  ..     ,  .    . 

electrical  con-  All  atoms  of  matter  are  regarded  as  origi- 
datoms°^  nally  charged  with  either  positive  or  nega- 
tive electricity.  Hydrogen  and  the  metals 
are  electro-positive  ;  oxygen,  chlorine,  and  cyanogen, 
and  other  substances,  to  be  described  hereafter,  are  ne- 
gative. A  molecule  of  water  is  made  up  of  a  positive 
atom  of  hydrogen,  and  a  negative  atom  of  oxygen  ; 
hydrochloric  acid,  of  positive  hydrogen  and  negative 
chlorine  ;  oxide  of  silver,  of  positive  silver  and  nega- 
tive oxygen.  The  figure,  in  which  +'  represents 
positive  and  —  negative,  may  represent  a  mole- 
cule of  either  of  the  compounds  named. 

252.  QUANTITY  OF  ELECTRICITY. — The 

What  quanti-  . 

ty  of  electrid-  quantity  of  electricity  thus  combined  or 
Ziwa™rt?ned  neutralized,  in  almost  all  kinds  of  matter, 
is  enormous.  Faraday  has  shown  that 
a  drop  of  water,  contains  more  than  is  discharged  in 
the  most  violent  flash  of  lightning. 


The  terms  atomt  and  molecule,  .ire  synonymous.     But  "molecule"  is 
limited,  in  the  present  work,  to  the'particle  of  a  compound. 


GALVANIC    ELECTRICITY. 


105 


253.  DECOMPOSITION  OF  WATER.  —  If  the 

Describe  the  ..  . 

decomposition    electrodes  are  immersed  in  water,  as  repre- 

of  water.  ^^    in  the    figur^  the 

water  is  decomposed,  and  separated 
into  its  elements.  Bubbles  of  hydro- 
gen collect  on  the  negative  electrode, 
and  bubbles  of  oxygen  on  the  posi- 
tive, and  finally  disengage  themselves, 
and  rise  through  the  water. 

254.  It  is  to  be  observed  that  positive 

Why  does  hy-     .       ,  -1-1 

drogen  appear    hydrogen  is  liberated  at  the  negative  pole, 


as  if  the  latter  had  a  Power  analogous  to 
that  of  the  magnet  for  iron,  to  draw  the 
hydrogen  out  of  the  water,  in  which  it  exists  combined. 
On  the  other  hand,  negative  oxygen  is  liberated  at  the 
positive  pole,  as  though  the  latter  had  the  same  attrac- 
tive power  for  oxygen.  The  above  figure  is  given 
solely  for  the  purpose  of  illustration.  The  actual  form 
of  apparatus  for  decomposing  water,  by  the  galvanic 
current,  is  described  in  a  subsequent  paragraph. 

255.   THEORY  OF  THE  DECOMPOSITION  OF 

Give  the  theo-  . 

ry  of  the  de-  WATER.  —  It  is  a  remarkable  circumstance, 
™™%!sition  °f  in  the  decomposition  just  described,  that  it 
continues  to  occur  even  when  the  elec- 
trodes are  quite  widely  separated  from  each  other.  Now, 
a  molecule  of  water  is  extremely 
small,  and  cannot  occupy  the  space 
between  the  electrodes,  if  they  are 
separated  to  any  considerable  ex- 
tent. The  space  must  be  occu- 
pied by  many  such  particles,  which, 
5* 


106  GALVANIC    ELECTRICITY. 

for  the  sake  of  definiteness,  we  will  conceive  of  as  ar- 
ranged in  straight  lines,  between  the  two  electrodes. 
The  circles  iiUhe  figure,  inscribed  H  and  O,  represent 
one  of  these  lines  of  molecules.  The  difficulty  now 
arises,  to  account  for  the  fact,  that  when  the  hydrogen  is 
liberated  at  the  negative  pole,  the  oxygen,  combined 
with  it  a  moment  before,  is  not  also  liberated  at  the  same 
point.  The  view  to  be  taken  of  it  is  as  follows  :  that  as 
soon  as  the  atom  of  oxygen  loses  its  hydrogen,  it  combines 
with  the  hydrogen  of  the  next  molecule  of  water. 
The  oxygen  of  this  second  one  being  thereby  liberated, 
combines  with  the  hydrogen  of  the  next ;  and  this 
decomposition  and  recomposition  continues  throughout 
the  series.  The  end  of  the  series  being  reached,  the 
last  oxygen  atom  escapes  in  the  form  of  gas.  The  action 
being  simultaneous  throughout  the  series,  this  evolution 
occurs  at  the  instant  that  the  hydrogen  is  set  at 
liberty  at  the  negative  electrode.  It  is,  therefore, 
quite  as  proper  to  give  the  explanation  of  the  diffi- 
culty first  stated,  by  beginning  with  the  liberation  of 
oxygen  at  the  positive  electrode,  and  supposing  the 
hydrogen  to  combine  with  the  oxygen  of  the  next 
molecule  of  water  in  the  series,  and  so  on  to  the  nega- 
tive electrode,  where  hydrogen  is  evolved.  The  ac- 
tion is,  in  fact,  as  before  stated,  simultaneous. 

256.  DEPOSITION  OF  METALS. — The  me- 

Explain  the  .  .  . 

deposition  of     tals  are  electro-positive.    Oxygen,  chlorine, 

™niLbygal'    &c''  on  the  other  hand>  are  negative.     If, 

therefore,    oxides,   chlorides,  or   cyanides 

of  the    metals   are    subjected   to    the  action    of    the 

electrodes,    they   are    decomposed,    while    the   metal 


ELECTRO-PLATING.  107 

goes  to  the  negative,  and  the  oxygen,  chlorine,  or 
cyanogen,  to  the  positive.  But  the  metals,  when  sepa- 
rated from  their  combinations,  being  solid  bodies,  can- 
not escape.  They  collect  on  the  negative  electrode,  in- 
stead. If  this  be  attached  to  a  brass  spoon  or  fork,  or 
any  other  object  it  is  desired  to  plate,  the  spoon  be- 
comes itself  the  electrode,  and  the  metal  is  deposited 
upon  it  as  long  as  the  action  of  the  battery  continues. 
At  the  same  time,  the  oxygen,  or  other  negative  ele- 
ment, goes  to  the  positive  electrode,  generally  cor- 
roding it,  instead  of  passing  off  as  gas. 

257  .  SILVERING    APPARATUS. — The    re- 

W hat  appara-          . 

tue  is  required   quirements  for  electro-silvering  or  gilding, 

are  first>  a  batterY  of  somewhat  different 

form  from  that  already  described,  though 
precisely  the  same  in  principle  ;  second,  an  acid  to  ex- 
cite it  ;  and  third,  a  solution  containing  gold  or  silver. 
These  will  be  described  in  turn. 

258.  A  convenient  form  of  the 
apparatus  is  represented  in  the  fig'i 
are,  and   may  be   prepared  from 
sheet  zinc  and  copper  in  a  few  mo- -^ 
ments.     It  consists  of  a  bent  strip 

of  the  former  metal,  with  a  strip  of  copper 
thc      fastened  between  the   two  portions.    The 

metals  should  be  within  an  eighth  of  an 
inch  of  each  other,  but  without  contact.  To  secure 
this,  they  are  tied  together  with  thread,  bits  of  wood  or 
cotton  cloth  being  previously  interposed.  Copper 
wires  being  attached  to  the  zinc  and  copper,  as  rep- 
resented in  the  figure,  the  apparatus  is  placed  in  a  com- 
mon tumbler,  and  the  battery  is  complete. 


108  GALVANIC    ELECTRICITY. 

259.  Before  combining  the  battery  as 

How  and  why  ...... 

is  the  zinc         above    described,  it  is  best   to    wash  the 


zinc  with  soaP  and  water>  and  afterward 
with  dilute  sulphuric  acid,  and  then  to 
immerse  it  for  half  a  minute  or  so  in  a  solution  of  ni- 
trate of  mercury.  By  this  process,  the  zinc  acquires 
a  thin  film  of  quicksilver,  which  afterward  protects  it 
from  the  action  of  the  acid  used  to  excite  the  battery, 
excepting  when  the  current  is  completed.  When  the 
battery  is  in  operation,  it  also  has  the  effect  of  making 
the  action,  more  equal  and  constant.  It  is  then  to 
be  again  washed,  and  newly  immersed  in  the  acid  solu- 
tion. This  solution  is  prepared  by  dissolving  quicksil- 
ver, of  the  bulk  of  two  peas,  in  nitric  acid,  and  pouring 
the  clear  liquid  into  a  tumbler  of  water. 

260.  THE  EXCITING  ACID.  —  The   exci- 

How  is  the  ex-       .  . 

citing  acid  ting  liquid  is  dilute  sulphuric  acid,  consist- 
preparc  .  .^  ^  Qne  part  Q.J  ^  vitriol,  to  ten  parts  of 

water.  The  acid  is  poured  into  the  proper  quantity  of 
water,  and  set  aside  to  cool. 

261.  THE    SILVERING    SOLUTION.  —  To 

How  is  the  sil-  .  . 

vering  solution  make  a  half  pint  of  the  solution,  a  dime  is 
prepared?  placed  in  a  test-tube  and  dissolved  in  ni- 
tric acid,  the  solution  being  diluted  with  water.  Muri- 
atic acid  is  then  added,  which  precipitates  the  silver,  in 
the  form  of  a  white  curd.  This  is  allowed  to  settle,  and 
the  green  liquid,  which  contains  the  copper  of  the  coin, 
is  poured  off.  Water  is  again  added,  and  the  curd  al- 
lowed to  settle  ;  this  cleansing  process  is  several 
times  repeated.  The  test-tube  is  then  half  filled  with 
water,  and  heated,  and  bits  of  cyanide  of  potassium  ad- 
ded, until  a  transparent  solution  is  obtained. 


ELECTRO-PLATING.  109 

262.  A  solution  for  gilding,  is  prepared 

How  is  the  so-  "       _ 

lutionfor  ,  by  drying  a  solution  of  gold,  at  a  moderate 
heat>  and  dissolving  it  in  cyanide  of  po- 
tassium, as  above  described.  The  process 

for  gilding,  is  in  all  respects  the  same  as  that  for  the 

deposition  of  silver. 

263.  THE  PROCESS.  —  The  battery   and 

How  is  the  sil-       .... 

veriny  process    silvering  solution  being  prepared,  the  cop- 
conducted?        ^  CQ^  or  ^j^  object  to  be  silvered,  is 


cleansed  with  potash,  rubbed  with  chalk  or  rotten- 
stone,  and  then  attached  to  the  wire  proceeding  from 
the  zinc.  A  silver  coin  is  fastened  to  the  other  wire, 
and  immersed  in  the  silvering  solution  ;  acid  is  then 
added  to  excite  the  battery,  and  the  object  to  be  silvered 
is  lastly  immersed.  It  should  be  hung  face  to  face  with 
the  silver  coin,  and  quite  near  to  it,  the  two  being  kept 
in  their  places  by  blocks  placed  across  the  tumbler,  as 
represented  in  the  figure.  The  coin  will  receive  a  per- 
ceptible coatingwithin  a  few  minutes,  and  will  be  more 
thickly  covered,  according  to  the  time  of  immersion. 
The  deposit  is  hastened  by  keeping  the  solution  mode- 
rately warm.  This  is  especially  advantageous  in  the 
commencement  of  the  process.  The  newly  plated  sur- 
face is  without  lustre,  and  requires  burnishing  after  re- 
moval from  the  solution. 

264.   OBJECT  OF  THE  SILVER  COIN.  —  The 

What  is  the 

object  of  the  piece  of  silver  is  attached  to  the  positive 
wire,  to  maintain  the  strength  of  the  solu- 
tion. It  is  eaten  away,  and  dissolved  as  fast  as  silver 
is  deposited  on  the  objects  connected  with  the  negative 
wire.  The  reason  of  this  is,  that  the  cyanogen  of  the 


110  GALVANIC    ELECTRICITY. 

solution,  when  it  goes  to  the  positive  pole,  as  before  ex- 
plained, combines  with  silver,  forming  new  cyanide  of 
silver,  which  dissolves  and  mixes  with  the  rest.  Thus, 
the  strength  of  the  solution  is  always  maintained.  The 
coin  is  attached  to  the  negative  wire,  by  flattening  the 
latter,  laying  it  on  the  back  of  the  coin,  and  covering 
the  whole  with  sealing  wax ;  the  coin  and  wire  should 
be  previously  slightly  warmed,  and  the  wax  used  at  a 
moderate  heat,  so  that  it  shall  not  run  between  the  wire 
and  the  coin,  and  prevent  their  perfect  contact. 

How  are  med-          265.    COPYING    OF    MEDALS. If  it    IS  de- 

ais  copied?  sired  to  copy  the  face  of  a  medal  or  a  coin, 
the  same  apparatus  suffices.  The  reverse  and  edges  of 
the  coin  are  very  slightly  oiled,  to  prevent  the  adhesion 
of  the  copy  about  to  be  made.  It  is  then  placed  in  the 
solution.  The  metal  deposits  upon  it,  copying  perfectly 
every  elevation  and  depression.  When  the  crust  is  suffi- 
ciently thick,  which  will  be  after  the  lapse  of  twelve 
hours,  the  coin,  with  its  shell  of  metal,  is  removed,  and 
the  whole  process  repeated  with  the  mould.  The  de- 
posit which  now  forms  in  the  shell,  is  an  exact  copy  of 
the  face  of  the  original  coin.  Moulds  are  also  made  by 
stamping  the  coin  into  soft  metal,  and  using  the  impres- 
sion thus  produced  instead  of  the  copper  shell.  Copper 
plates,  for  engravings,  may  be  copied  so  perfectly  by 
this  method,  as  to  be  fully  equal  to  the  original. 
How  are  wood  266.  COPYING  OF  WOOD  CUTS. — The  diffi- 
cuts  copied?  culty  of  copying  other  than  metallic  ob- 
jects, by  the  processes,  that  they  are  not  generally  good 
conductors.  Thus,  when  a  wood  cut  is  attached  to 
the  negative  wire,  it  does  not  itself  receive  a  nega- 


ELECTRIC    LIGHT.  Ill 

live  character  from  the  wire,  and  will  not,  therefore, 
take  positive  metal  from  the  solution.  This  is  obvia- 
ted by  covering  the  block  with  a  fine  powder  of  plum- 
bago or  black  lead,  which  has  high  conducting  power. 

267.  This  process  is  very  extensively 

It  what  cases  r  / 

is  the  process  practised.  Where  a  large  number  of  cuts 
pra  of  the  same  kind  are  wanted,  as  for  exam- 

ple, to  print  labels  for  dry  goods,  only  one  engraving 
on  wood  is  made,  and  numerous  copies  are  taken  by 
the  above  process,  which  is  much  less  costly. 

268.  HEATING  EFFECTS    OF    THE   CUR- 

Descrtbe  the 

heating  e/ect  RENT. — If  the  electrodes  are  connected 
of  Recurrent?  while  the  battery  js  jn  actlOn,  the  wire  be- 

comes  heated  more  or  less  strongly,  according  to  the 
size  of  the  plates.  If  the  plates  are  very  large,  the 
wire  melts,  even  though  it  be  of  platinum,  the  most 
infusible  of  metals.  Gold  may  even  be  converted  in- 
to vapor  by  the  same  means.  Carbon,  supposed  a  few 
years  since  to  be  entirely  infusible  may  be  also  super- 
ficially fused,  and  even  volatalized  between  the  electro- 
des. It  condenses  again  at  a  little  distance,  in  the  form 
of  microscopic  crystals.  Imperfect  diamonds  have  been 
thus  artificially  produced.  With  such  a  battery  as 
has  been  described  the  elevation  of  temperature  would 
be  scarcely  perceptible. 

269.  THE  ELECTRIC  LIGHT. — If  the  current 

How  is  the  . 

electric  light  be  allowed  to  pass  between  two  points  of 
produced  ?  prepared  charcoal,  an  exceedingly  intense 
light  is  produced,  accompanied  by  great  heat.  Char- 
coal is  employed  because  it  is  a  comparatively  infu- 
sible, and  inferior  in  conducting  power.  A  metallic 


112  GAI  VANIC    ELECTRICITY. 

wire,  under  the  same  circumstances,  would  melt,  or  if 
too  large  to  undergo  fusion,  would  allow  the  current  to 
flow  readily  through  it,  without  that  detention  which  is 
essential  to  the  production  of  the  above  effects,  in  their 
highest  degree. 

270.  If    the  charcoal   points  be  with- 

How  ts  the  '  ,        ,  .  -, 

electric  flame  drawn  from  each  other,  a  splendid  electric 
produced?  flame  is  produced  between  them.  This 
flame  is  not  the  result  of  combustion,  for  the  char- 
coal is  extremely  dense,  and  wastes  away  but  slow- 
ly. It  is  purely  electric.  Metals  melt  in  it,  and  are 
dissipated  in  vapor.  A  much  larger  battery  than  that 
here  described,  is  requisite  fox  the  production  of  ei- 
ther the  light  or  flame.  In  experimenting  with  the 
compound  battery,  hereafter  described,  a  slight  spark 
will  be  observed,  on  separating  the  electrodes. 

271.  DECOMPOSITION  IN  THE   BATTERY. 
A  decomposition,  similar   to  that    of  wa- 


in the  battery  ter  and  metallic  compounds,  as  above  de- 
scribed, takes  place  in  the  battery  itself, 
and  seems  to  be  the  source  of  its  power.  Suppose,  for 
example,  the  acid  with  which  the  zinc  and  copper  are 
in  contact,  to  be  hydrochloric,  each  molecule  of 
which  is  composed  of  an  atom  of  hydrogen  and 
an  atom  of  chlorine.  The  zinc  becomes  positive 
where  it  is  in  contact  with  the  acid,  and  negative  at 
the  other  end,  the  extremities  assuming  different  states, 
as  in  the  case  of  a  piece  of  soft  iron  suspended  from  a 
magnet.  The  outer  portion  of  the  copper  being  in  con- 
tact with  the  negative  end  of  the  zinc,  is,  itself,  nega- 
tive, while  the  end  immersed  is  positive.  The  atoms 


GALVANIC    ELECTRICITY.  113 

composing  the  acid,  are  supposed  to  be  arranged  as  rep- 
resented in  the  figure.  The  alternation  of  positive  and 
negative,  in  copper,  zinc,  and  the  line  of  acid  molecules 
is  analogous  to  the  case  of  the  sus- 
pended keys.  As  long  as  the  metals 
are  immersed,  and  made  to  touch,  an 
atom  of  zinc  constantly  combines 
with  an  adjacent  atom  of  chlorine. 
It  follows,  that  no  chlorine  is  set  at 
liberty.  As  fast  as  each  atom  unites 
with  the  zinc,  its  hydrogen  combines 
with  the  next  chlorine,  the  hydrogen  of  this,  with 
the  next,  and  so  on,  as  before  explained,  in  the  de- 
composition of  water.  Hydrogen  is  therefore  con- 
stantly given  off  at  the  surface  of  the  copper.  But 
when  the  two  metals  are  not  in  contact  above  the  li- 
quid, and  the  circuit  is,  consequently,  not  completed, 
there  is  no  negative  influence  exerted  at  the  extremity 
of  the  copper,  and  the  series  of  decompositions,  before 
described,  does  not  occur. 

272.    A    SALT    EMPLOYED    AS   EXCITANT 

Explain  how  .  •-,,  -iini 

a  battery  can  It  is  not  essential,  that  an  acid  shall  be  used 
bamit?ed  by  as  tlie  excitmg  liquid  iii  the  galvanic  bat- 
tery. A  metallic  salt  is  sometimes  em- 
ployed. This  may  be  best  illustrated,  by  supposing 
chloride  of  copper  to  be  employed  instead  of  hydrochlo- 
ric acid,  which  is  chloride  of  hydrogen.  The  chlo- 
rine goes  to  the  zinc,  as  in  the  previous  case,  and  the 
copper  of  the  salt,  to  the  strip  of  copper,  placed  in  the 
solution.  Being  a  solid,  it  remains  there,  and  en- 
crusts the  copper,  instead  of  being  evolved,  as  in  the 
case  of  hydrogen. 


114 


GALVANIC    ELECTRICITY. 


273.   DIFFERENT  KINDS  OF  BATTERIES.— 

What  is  said  .     ..  . 

o/  the  differ-  There  are  different  kinds  01  galvanic  bat- 
britertef  teries,  but  the  principle  in  all  is  the  same. 
Two  of  the  forms  in  most  common  use 
are  described  in  the  Appendix.  Smee's  battery  is 
especially  recommended  to  the  student,  for  its  cheap- 
ness, simplicity,  and  efficiency.  It  is  very  similar,  as 
will  be  seen,  to  the  simple  one  which  has  been  already 
described. 


274.   COMPOUND  CIRCUIT. — For  the  sake 

What  is  said        f     .        ,.    .  „     .       f 

of  the  com-  ot  simplicity,  all  the  foregoing  decomposi- 
pound circuit?  tions have  been  described,  as  a  result  of  the 
action  of  a  simple  voltaic  circle,  consisting  of  an  acid, 
and  two  metals.  But,  it  is  found  that  in  many  decom- 
positions, the  power  of  such  a  battery  is  insufficient. 
The  efficiency  is  increased  by  employing  several  single 
batteries  together,  and  bringing  them  all  to  bear  upon 
the  same  electrode. 

How  are  heat-  275.  The  heating  and  magnetic  effects 
ing  and  mag-  f  fa  battery  are  very  ^cft  increased  by 

netic  effects  J  J  J 

produced?  uniting  the  plates,  as  in  the  preceding  fig- 
ure, where  all  the  zinc  plates  are  joined  together,  so  as 
virtually  to  form  one.  The  quantity  of  the  current  is 
thus  increased.  Power  of  decomposition,  and  to  give 
shocks,  such  as  are  taken  from  an  electrical  machine, 


GALVANIC    ELECTRICITY. 


115 


are   increased  by  uniting  them  as  in  the  figure  which 
follows.     The  intensity  of  the  current  is  thus  increased. 


What  is  the 
meaning  of  in- 
tensity ?     Of 
quantity  ? 


276.  MEANING  OF  INTENSITY  AND  QUAN- 
TiTY. — The  terms  intensity  and  quantity 
are   rather  vaguely  used,  and  do  not  de- 
scribe as  definitely  as  may  be  desired,   the 

different  properties  of  the  current.  The  student  must 
associate  the  term  quantity  with  increased  heating  and 
magnetic  effects,  and  the  term  intensity,  with  power 
of  decomposition. 

277.  DECOMPOSITION  BY  THE  COMPOUND 

Explain  the  ... 

apparatus  for    CIRCUIT. — Jb  or  the  decomposition  oi  water, 

a  S6rieS  °f   Slx  CUPS>  Sllch    aS  haVG  beetl  al- 

ready  described  for  use  in  plating,  will  suf- 
fice. They  are  to  be  united  according  to  the  second  ar- 
rangement. The  zinc  of  each  cup  is  to  be  connected  with 
the  copper  of  the  next  in  order,  by  a  copper  wire,  forming 
a  good  metallic  contact.  This  being  done,  another  long 
wire  is  fastened  to  the  first  copper  plate,  and  one,  also,  to 
the  last  zinc,  and  bits  of  platinum  wire  or  foil  are  attached 
to  their  ends.  A  small  test-tube  is  then  filled 
with  acidulated  water,  and  inverted  in  a  cup, 
also  containing  water  and  acid.  The  wires 
are  bent  upward  into  the  cup,  as  represented 
in  the  figure.  The  battery  being  now  set  in 
operation,  by  dilute  acid,  as  before  described, 


116  GALVANIC    ELECTRICITY. 

the  evolution  of  gas  immediately  commences  from  the 
the  platinum  wires.  This  compound  battery  will  be 
found  rather  slow  in  its  operation,  and  has  been  de- 
scribed only  for  the  purpose  of  illustrating  the  use  of 
the  more  powerful  galvanic  batteries  of  similar  con- 
struction. The  student  is  advised  to  substitute  for  it 
the  Voltaic  pile,  as  hereafter  described. 

278.    AN  EXPLOSIVE  MIXTURE.  —  A  mix- 

What  proper-  „  ,       , 

ty  has  the         ture  of  hydrogen  and  oxygen  gases,  in  the 


US  proportion  m  which  they  are  here  evolved, 
is  explosive.  This  property  is  the  evi- 
dence that  the  gases  are  really  oxygen  and  hydrogen, 
in  due  proportion.  A  sufficient  quantity  being  col- 
lected, the  mouth  of  the  tube  is  covered  with  the  finger, 
the  tube  inverted,  and  a  match  applied  at  the  mouth. 
A  slight  puff  is  all  the  evidence  that  will  be  obtained 
from  a  small  quantity  of  the  mixture.  A  test-tube  full 
will  give  a  sharp  report. 

279.      SEPARATE    COLLECTION    OF  THE 

How  may  the  ,  .  , 

gate*  be  col-       GASES.  —  By  using  two  test-tubes,  instead 

lected*cpa-        of  before  described,  and  introduc- 

rately  ? 

ing  an  electrode  into  each,  the  gases  may 

be  separately  collected  and  tested  by  the  methods  give 
in  the  section  which  treats  of  those  gases. 

280.  The  water  is  acidulated  in  the  ex- 

Wky  is  the  . 

water  to  be  de-  penment,  to  make  it  a  better  conductor  of 
"dilated?  the  mmience  which  must  pass  through  it, 
from  one  electrode  to  the  other,  in  order 
that  the  decomposition  may  take  place.  The  reason 
for  using  platinum  electrodes  has  already  been  given. 
In  the  present  case,  if  the  copper  wires  themselves 


GALVANIC    ELECTRICITY.  117 

were  introduced,  the  negative  electrode  would  appro- 
priate all  the  oxygen  to  itself,  thereby  becoming  grad- 
ually converted  into  oxide  of  copper,  and  nothing  but 
hydrogen  gas  would  be  obtained. 

281.    DECOMPOSITION  OF  A  SALT. — The 
Describe  the      decomposition   effected    by   the    galvanic 

decomposition  *  ° 

of  a  salt.  current,  may  be  more  strikingly  illustrated 
by  introducing  the  electrodes  into  a  dilute 
solution  of  sal-ammoniac,  previously 
colored  by  litmus,  or  red  cabbage. 
Chlorine  is  liberated  at  the  positive 
pole,  and  bleaches  the  solution  in  its 
vicinity,  while  ammonia  is  evolved 
with  hydrogen,  at  the  negative  pole, 
and  changes  the  color  of  the  solution  from  blue  to  red. 
That  of  the  cabbage  is  changed  by  the  same  means, 
from  red  to  green.  By  employing  a  glass  box  with  two 
compartments,  such  as  is  represented  in  the  figure,  the 
two  portions  of  the  liquid  may  be  kept  distinct.  It  is 
essential,  for  reasons  that  will  be  understood  from  the 
preceding  paragraph,  that  there  be  an  unbroken  chain 
of  molecules  of  the  electrolyte,  or  substance  to  be  de- 
composed, between  the  electrodes.  This  is  effected  by 
making  the  partition  quite  loose,  and  keeping  it  in  its 
place  by  strips  of  paper,  placed  along  the  edge.  All  the 
communication  that  is  essential,  then  takes  place  through 
the  pores  of  the  paper,  while  the  partition  at  the  same 
time  prevents  the  mixing  of  the  contents  of  the  sepa- 
rate cells.  The  same  object  may  be  accomplished  by 
the  employment  of  two  tea-cups,  holding  the  liquids, 
and  connected  by  moistened  lamp-wick  ;  a  larger  pile, 


118  GALVANIC    ELECTRICITY. 

and  a  longer  time,  is  in  this  case  required  to  effect  the 

decomposition.     The  glass  box  may  be  made  according 

to  the  directions  given  in  paragraph  33  for  making  a 

prism. 

Describe  the          282.     THE  VOLTAIC    PILE.  —  The    first 

Voltaic  pile,      form  of  galvanic  battery  ever  produced  is 

represented  in  the  figure,  and  is  called  the 

Voltaic  pile,  from  the  name  of  its  inventor. 

It  consists  of  a  succession  of  discs  of  zinc, 

copper,  and  cloth,  moistened  with  acid,  al- 

ternating with  each  other,  as  represented 

in  the  figure.     Each  series  forms  a  simple 

battery,  and  the   whole  pile  is  a  compound 

battery,  essentially  the  same  as  that  before 

described.     Wires  to  serve  as  electrodes  are  to  be  at- 

tached to  the  extreme  copper  and  zinc. 

283.  The  enlarged  form  of  the  Voltaic 

What  is  said         .,  „  .... 

of  the  en-         pile  represented  in  the  next  figure  will  be 


Voltaic  found  a  mogt  efficient  apparatus  for  ef- 
fecting decomposition.  It  is  composed  of 
sixteen  plates  of  each  metal,  each  having  a  surface 
of  twelve  square  inches.  The  zinc  should  be  amalga.- 
mated,  as  before  explained.  Flannel,  or  any  similar 
material  may  be  employed  to  separate  the  plates.  With 
this  piece  of  apparatus,  the  spark  is  readily  obtained,  and 
slight  shocks  may  be  taken  by  bringing  the  two  hands 
into  contact  at  the  same  moment 
with  the  top  and  bottom  of  the  pile. 
On  terminating  the  electrodes  with 
fine  iron  wire,  and  frequently  uni- 
ting and  separating  them,  scintil- 


ELECTRO-MAGNETISM.  119 

lations  of  the  burning  metal  may  also  be  readily  pro- 
duced. By  increasing  the  number  of  the  plates  still 
more  striking  effects  are  obtained.  With  a  pile  con- 
sisting of  six  or  eight  plates  a  foot  square,  platinum 
wire  connecting  the  electrodes  may  be  readily  fused. 
Such  a  battery  is  also  more  effectual  in  the  electro- 
magnetic experiments  which  follow. 

Describe  the  284.  MAGNETIC  PROPERTIES  OF  THE  CUR- 

magnetic  pro-    RENT> — jf  the  wire  connecting  the  zinc 

perties   of  the 

galvanic  cur-     and  copper  of  the  galvanic  battery  be  wound 
in  a  spiral,  as  represented  in  the  figure,  the 
coil,  or  helix,  as  it  is  termed,  be- 
comes   possessed   of    magnetic 
properties.     Like  a  magnet,  it  attracts  iron,  and  other 
magnets,  and  according  to  the  same  laws. 
How  may  a  285.  THE  SUSPENDED  BAR. — A  rod  of  iron 

^  °endedlne  Drougnt  near  one  °f  tne  extremities  of  the 
the  air  ?  coil,  is  not  only  attracted,  but  actually 

lifted  up  into  the  centre  of  the  coil,  where  it  re- 
mains suspended  without  contact,  or  visible  sup- 
port, as  long  as  the  battery  continues  in  action. 
Science  has  thus  realized  the  fable  of  Mahomet's 
coffin,  which  was  said  to  have  been  miraculously 
suspended  in  the  air.  The  helix,  for  this  and 
similar  experiments,  is  wound  closer  than  is  rep- 
resented in  the  figure,  and  is  composed  of  several 
layers  of  wire.  A  powerful  battery  is  also  essential  to 
success  in  this  experiment. 

286.    POLARITY    OF    THE    COIL. — That 

What  is  the  •'•••,  i      • 

action  of  a  such  a  coil  has  polarity,  may  be  proved, 
precisely  as  with  a  magnet.  One  end  of 
it  attracts  the  north  pole  of  a  magnet,  and 


120 


GALVANIC    ELECTRICITY. 


is  therefore  a  south  pole.  The  other  end 
attracts  the  south  pole  of  a  magnetic  nee- 
dle, and  is  therefore,  itself,  a  north  pole- 
But  the  direction  in  which  the  current 
moves  round  in  the  helix,  determines 
which  shall  be  north,  and  which  south.. 
As  the  current  is  represented  to  move 
in  the  first  of  the  two  coils  in  the  figure,  the  up- 
per end  of  the  coil  is  north,  and  the  lower  end  south. 
If  it  is  made  to  move  in  the  other  direction,  as  in 
the  second  figure,  the  poles  are  reversed. 

287.     CONSEQUENT    MOTION    or  A  sus- 

Hoio  may  we 

obtain  motion  FENDED  COIL. — To  obtain  motion  of  the 
°/eifke  C°d  li~  coil  itself>  as  a  consequence  of  its  magne- 
tism, it  is  necessary  to  suspend  it ;  and  in 
order  to  suspend  it  with  perfect  freedom  of  motion,  it  is 
necessary  to  suspend  the  battery 
with  it.  Such  a  suspended  coil 
and  battery  is  represented  in  the 
figure.  In  preparing  it,  the  wire 
is  wound  forty  or  fifty  times 
round  a  test-tube,  (which  is  afterward  removed,)  and 
copper  and  zinc  plates  then  attached  to  the  ends. 
The  plates  are  tied  together  with  several  layers  of  paper 
between  them,  then  dipped  in  acid,  and  the  apparatus 
carefully  suspended  by  an  untwisted  silk  fibre.  The 
acid  absorbed  by  the  paper,  suffices  to  maintain  for 
some  time  the  action  of  the  battery.  On  approaching 
a  magnet  to  either  pole  of  the  suspended  coil,  it  is  at- 
tracted or  repelled  precisely  as  if  it  were  a  magnet.  In- 
stead of  suspending  the  apparatus  by  a  thread,  it  may 


ELECTRO-MAGNETISM.  121 

be  floated  on  acidulated  water,  by  means  of  a  cork, 
and  submitted  to  the  same  experiment.  In  this  con- 
struction, the  wires  proceeding  from  the  end  of  the 
coil,  pass  through  the  cork,  before  connecting  with  the 
•metallic  plates.  The  first  described  method  of  suspen- 
sion is  regarded  as  the  best. 

288.   THE  COIL  A  MAGNETIC  NEEDLE.— 

How  may  the 

coil  be  conver-    On    floating    a  coil    with    extreme    deli- 


<=acy  upon  water,  and  protecting  it  from 
all  currents  of  air  and  water,  it  assumes 
north  and  south  direction,  and  becomes,  in  fact,  a  mag- 
netic needle.  This  can  only  be  accomplished  by 
means  of  a  light  glass  cup,  blown  for  the  especial  pur- 
pose, and  prolonged  into  a  cone  below,  to  give  it  stead- 
iness in  the  water.  This  cup  is  filled  with  dilute  acid, 
in  which  the  plates  are  immersed,  and  is  then  floated 
in  a  larger  vessel. 

289.  MUTUAL  ACTION  OF  COILS.  —  Two 

Describe  the  . 

mutual  action    helices,  or  coils,  such  as  are  described  in 


the  last  paragraph,  floating  near  each  other, 
attract  or  repel,  precisely  as  if  they  were 
magnets,  according  as  like  or  unlike  poles  are  brought 
together.  They  finally  attach  themselves  to  each 
other  in  the  position  represented  in 
the  figure,  lying  parallel  and  with 
opposite  poles  in  contact.  In  this 
position,  it  will  be  observed,  that  at  thepoint  of  con- 
tact, the  currents  are  moving  in  the  same  direction. 
The  attraction  of  the  unlike  poles,  may  be  regarded, 
then,  as  a  consequence  of  the  attraction  of  like  cur- 
rents. For  it  is  found  to  be  universally  true,  that 

6 


122  GALVANIC    ELECTRICITY. 

currents  moving  in  the  same  general  direction,  attract 
each  other,  while  those  moving  in  opposite  directions, 
repel. 

What  is  the  290.    MUTUAL    ACTION    OF  COIL  AND    MAG- 

mutual  action    NET — jf  a  floating  magnet  be  substituted 

of  a  coil  and 

magnet?  for  one  of  the  coils,  in  the  above  ex- 

periment, the  result  is  not  in  the  least  affected. 
They  act  toward  each  other  precisely  as  if  both 
were  magnets,  or  both,  coils. 

291.  ACTION  OF  A  SINGLE  WIRE  ON 

What  is  the  .       , 

action  of  sin-    A  COIL.— A  single  wire,  carrying  a  cur- 

yle  wire  on  a  rent  actg  Qn  &  floatmcr  coil  in  the  same 
magnetic  coil  r 

manner.     Stretched  above  it,  as  in- 
dicated in  the  figure,  the  north  pole  of  the  coil 
will  move  to  the  right.     The  motion  is  such  as  to  bring 
adjacent  currents,  in  the  wire,  and  in   the  coil,  to  co- 
incide in  direction. 

292.  POLARITY  OF  THE  COIL    IMPARTED 

What  effect  f 

has  the  mag-  TO  IRON. — A  bar  of  soft  iron  placed  in 
neticcoil  upon  tk  Q-i  becornes  itself  a  magnet,  and  re- 

metals  ? 

ceives  the  name  of  electro-magnet.    Great- 
er power  is   acquired   if   the  metal   is,  closely 
wound  with  copper  wire,  covered  with  cotton3 
to    prevent  any  lateral  passage   of    the    current. 
The  horse-shoe  shape,  in   which  the  poles  are 
brought  round  near  to  each  other,   is  the  more 
common.       The  power  of  such  magnets  contin-' 
tinues  only  while  the  current  is  passing.     Electro-     p 
magnets  have  been  constructed  capable  of  lifting  a  ton, 
or  even  more.     They  are  sometimes  employed  in  dress- 
ing iron  ores,  to  separate,  by  their  attraction,  the  work- 


ELECTRO-MAGNETISM.  123 

able  ore  from  the  refuse  earth  with  which  it  is  mixed. 
A  steel  bar  introduced  into  the  helix  while  the  current 
is  passing,  becomes  permanently  magnetic.  Permanent 
magnets,  are  now  commonly  made  in  this  manner. 

293.  PERMANENT  MAGNETISM  OF   STEEL. 

What  effect 

has  the  mag-     It    appears,   from  the  last  paragraph,  that 

"ted  I™11™1*™     a  bar  °f   S°ft    ir011    1S   a  magnet>  as  long  aS 

an  electrical  current  circulates  around  it. 
But  the  steel,  if  once  magnetic,  remains  so  permanent- 
ly. This  is  accounted  for,  by  supposing  that  the  cur- 
rent, in  the  wire,  excites  a  current  in  the  surface  of  the 
steel  itself,  which  continues  to  flow,  without  interrup- 
tion, after  the  wire  is  removed. 

294.  ACTION  OF  A  SINGLE  WIRE  ON 

What  is  the 

action  of  a  A  MAGNET. ^-A  wire,  carrying  a  cur- 
t  magnet?  °*  rent  in  the  direction  shown  in  the 
figure,  acts  on  a  magnet,  precisely  as 
on  a  floating  coil.  The  north  pole  of  the  mag- 
net is  made  to  deviate  to  the  east.  The  mo- 
tion is  such  as  to  bring  adjacent  currents  in  wire 
and  magnet  to  coincide. 

295.  ELECTRICAL  THEORY  OF  MAG- 

Explain  the  . 

electrical  theo-  NETisM. — According  to  this  theory,  all  mag- 
Ttlm?magne'  netism?  including  that  of  the  load-stone, 
the  magnetic  needle,  and  that  of  the  earth 
itself,  is  a  consequence  of  the  circulation  of  electrical 
currents.  In  the  earth,  such  currents  are  known  to  be 
excited,  and  kept  in  motion,  by  the  sun,  heating  in  turn 
successive  portions  of  its  surface.  They  flow  from 
east  to  west,  making  of  the  earth,  as  it  were,  an  im- 
mense coil,  or  helix.  In  magnets  they  are  also  in  con- 


124 


GALVANIC     ELECTRICITY. 


Explain  the 
figure. 


stant  circulation,  the  direction  being  dependent  on  the 
position  in  which  the  magnet  is  held.  In  the  case  of 
a  magnet  whose  north  pole  is  directed  north,  the  di- 
rection is  from  west  to  east  across  the  upper  surface, 
and  of  course,  in  the  contrary  direction  on  the  under 
side.  The  earth  acts  on  a  magnet,  or  a  floating  coil, 
as  one  helix  acts  on  another.  The  north  and  south 
direction  of  the  magnetic  needle  is  a  consequence  of 
this  action. 

296.  THE  THEORY  ILLUSTRATED. — In 
illustration  of  this  theory,  let  a  globe  be 
coiled  with  a  wire,  carrying  a  current,  as  indicated  in 
the  figure.  Let  the  current  flow  from  east  to  west 
through  the  coil.  A  small  magnetic  needle  placed  at 
different  points  on  the  surface 
of  the  globe,  however  the  po- 
sition of  the  latter  may  be 
changed,  will  always  point  to 
"its  north  pole.  It  is  under- 
stood, in  this  experiment,  that 
the  current  is  strong  enough 
to  overcome  the  influence  of 
the  earth  itself  on  the  mag- 
net. A  freely  movable  coil  through  which  a  current 
was  passing,  would,  in  this  case  also,  act  precisely  like 
a  magnet. 

297.  MAGNETIC    TELEGRAPH. — The   ex- 

Explain  the  .  . 

principle  of  planation  of  the  mechanism  of  the  mag- 
netic  teleg,raPh  belongs  to  Natural  Philoso- 
phy. The  principle  of  its  operation  may 


MAGNETIC    TELEGRAPH.  125 

be  here  given.  It  has  already  been  stated,  that  a  piece 
of  soft  iron  becomes  a  magnet,  when  a  current  of  elec- 
tricity circulates  in  a  coil  surrounding  it.  Now,  sup- 
pose the  two  ends  of  such  a  coil,  situated  in  a  distant 
city,  to  be  made  long  enough  to  reach  a  battery  in 
the  place  where  the  reader  resides,  and  to  be  stretched 
along  over  posts,  and  connected  with  the  poles  of  the 
battery.  The  current  occupies  no  perceptible  time  in 
its  passage.  Therefore,  as  soon  as  the  battery  is  set 
in  operation,  it  circulates  through  the  whole  extent 
of  the  wire,  and,  of  course,  through  the  coil  in  the 
distant  city.  The  piece  of  iron  which  it  incloses 
is  made  a  magnet,  and  will  immdiately  lift  its  arma- 
ture. If  the  current  is  stopped,  the  piece  of  iron  ceases 
to  be  a  magnet,  and  drops  its  armature.  But  the 
operator  at  the  battery  can  send  or  stop  the  current  at 
will,  by  simply  disconnecting  one  of  the  wires,  and 
thereby  lift  or  let  fall  the  armature  a  hundred  or  a  thou- 
sand miles  off,  as  often  as  he  pleases.  He  can  have 
an  understanding,  also,  with  the  person  in  the  distant 
city,  who  sees  the  motion  of  the  armature,  as  to  what 
it  shall  mean.  One  lift  may  indicate  the  letter  A  ;  two 
lifts,  the  letter  B  ;  and  so  on.  So  any  thing  may  be 
spelled  out,  and  it  thus  becomes  possible  to  commu- 
nicate ideas  by  electricity.  If  these  lifts  of  the  arma- 
ture can  be  made  to  record  themselves  on  a  slip  of 
paper,  the  further  advantage  of  writing  at  the  distant 
station  is  gained.  And  this  is  precisely  what  is  realized 
in  Morse's  telegraph,  and  more  particularly  described  in 
all  recent  works  on  Natural  Philosophy. 


126  GALVANIC  ELECTRICITY. 

298.   THE  EARTH,  USED  AS  A  CONDUCTOR. 

What  ^s  said 

of  the  earth       It  would  seem  requisite  to  extend  both  ends 

as^conduc-        of  the  wire    forming    the   coil    through    all 

the  intervening  distance,  and  then  to  con- 
nect them  with  the  opposite  poles  of  the  battery  ;  but 
it  is  found,  in  practice,  that  one  is  sufficient,  and  that 
all  the  middle  portion  of  the  second  wire  may  be  dis- 
pensed with.  The  remaining  ends,  one  connected 
with  the  helix,  and  the  other  with  the  battery,  being 
made  to  terminate  in  large  plates,  and  buried  in  the 
ground,  the  earth  between  them  is  found  to  take  the 
place  of  the  second  wire,  and  complete  the  circuit. 

Mention  some  299.    APPLICATIONS  OF  THE    TELEGRAPH. 

remarkable       There  are  many  applications  of  the  tele- 

applications  t 

of  the  tele-  graph  beside  the  one  of  transmitting  intel- 
graph.  ligence  to  distant  places.  In  the  city  of 

Boston,  an  alarm  of  fire  is  instantaneously  communi- 
cated throughout  the  city,  and  the  bells  rung  by  tele- 
graphic apparatus. 

In  Marseilles,  France,  a  single  clock  is  made  by  sim- 
ilar means  to  indicate  the  time  on  dials,  placed  in  the 
street  lamps  of  the  city.  Electro-magnetic  apparatus 
has  also  been  employed  with  the  most  remarkable  suc- 
cess in  increasing  the  dispatch  and  accuracy  of  astro- 
nomical observations  ;  making  it  possible  to  accomplish 
during  a  single  night  in  the  study  of  the  heavens,  what 
formerly  cost  a  month  of  labor. 

300.     PHYSIOLOGICAL  EFFECTS  OF  GAL- 

Describe  the 

physiological     VANisM. — The  nerves  of  animals  are  ex- 
fanismf?  ff<a'     tremel7  susceptible  to  the  galvanic  influ- 
ence.    The  apparatus  represented  in  the 


PHYSIOLOGICAL    EFFECTS.  127 

figure,  which  consists  of  strips  of  zinc  and  copper, 
three  inches  in  length,  separated  by  a  cork,  is  sufficient 
to  produce  convulsive  twitchings 
in  the  legs  of  a  frog  or  toad.  A 
larger  apparatus  produces  more  decided  effects.  The 
legs  are  to  be  employed,  with  a  portion  of  the  back 
bone  attached,  which  is  grasped  by  the  sharpened  ex- 
tremities of  the  galvanic  tweezers.  As  often  as  the 
circuit  is  completed,  by  bringing  the  other  extremeties 
into  contact,  by  the  pressure  of  the  fingers,  the  legs 
are  observed  to  twitch,  as  if  they  were  still  possessed 
of  life.  The  leg  of  a  grasshopper,  grasped  in  its 
thickest  part,  may  also  be  employed  in  the  experiment. 
In  both  these  cases,  the  moisture  of  the  flesh  or  skin 
is  the  exciting  fluid  of  the  galvanic  pair.  In  view  of 
the  destruction  of  life  which  they  involve,  these  expe- 
riments should  be  confined  to  the  lecture  room,  or  only 
made  where  many  persons  are  to  be  instructed  by  their 
exhibition. 

301.  DISCOVERY  OF  GALVANISM. — In  the 
discovery  of  words  of  Arago,  "  this  immortal  discovery 
galvanism  g^osQ  in  the  most  immediate  and  direct 

made  ? 

manner,  from  an  indisposition  with  which 
a  Bolognese  lady  was  affected,  in  1790,  for  which  her 
medical  adviser  prescribed  frog  broth."  The  frogs  had 
been  killed  and  skinned,  and  were  lying  on  the  table 
of  her  husband's  laboratory.  Experiments  were  in 
progress  with  an  electrical  machine,  which  stood  near 
tli em,  when  it  was  observed  that  the  frogs'  legs  were 
convulsed,  as  the  spark  passed.  This  was  not  a  new 
fact,  but  Galvani  was  not  acquainted  with  it,  and  un- 


128  GALVANIC    ELECTRICITY. 

dertook  to  find  out  the  cause.  In  preparing  for  the  in- 
vestigation, he  chanced  to  hang  the  hind  legs  of  seve- 
ral frogs,  by  copper  hooks,  from  the  iron  railing  of  the 
balcony  of  his  window.  As  often  as  the  wind,  or  any 
accidental  cause,  brought  the  muscles  into  contact  with 
the  iron  bar,  the  legs  were  convulsively  agitated.  The 
astonishment  of  the  experimenter  can  scarcely  be  con- 
ceived. In  undertaking  to  account  for  an  old  fact,  he 
had  stumbled  upon  a  most  important  discovery.  The 
theory  which  he  proposed  was  not  correct,  but  the  re- 
sults to  which  the  observation  have  since  led  are  as- 
tounding. The  telegraph,  the  electrotype,  and  many 
metals  discovered  by  galvanic  means,  may  all  be  re- 
garded as  its  offspring. 

302.     EXPLANATION. — The    convulsion 

Explain  the 

above  experi-  produced  in  this  case,  is  entirely  analagous, 
in  its  course,  to  that  described  in  the  last 
paragraph.  The  two  metals,  the  moist  muscle,  and 
the  wind,  to  produce  contact,  and  so  complete  the  cir- 
cuit, are  all  the  conditions  essential  to  the  production 
of  a  current,  and  consequent  contraction  of  the  nerves. 


INFLUENCE    OF    HEAT.  137 

magnesia  come  together,  they  unite  and  form  sulphate 
of  magnesia,  or  epsom  salt.  But  the  stimulus  of  heat 
is  often  required,  particularly  when  the  acid,  as  well 
as  the  oxide,  is  a  solid  substance.  The  affinity  be- 
tween acids  and  bases,  is  in  accordance  .with  the  gene- 
ral law,  that  chemical  attraction  between  substances  is 
strongest,  in  proportion  as  they  are  most  unlike,  or  op- 
pos3cl  to  each  other,  in  their  properties. 

324.  PROPERTIES  OF   ACIDS  AND  BASES. 

What  are  the  , 

properties  of  I  he  properties  of  these  two  classes  of 
acids  and  ba-  compOun(jSj  are  opposite,  and  when  brought 
together,  they  neutralize  each  other.  Thus, 
when  acid  and  soda  are  brought  together,  the  acid  taste 
of  the  former  and  the  alkaline  taste  of  the  latter,  both 
disappear.  Acids  change  certain  vegetable  blues  to 
red.  Bases  restore  the  color.  The  experiment  may 
be  made  with  an  infusion  of  litmus*  in  water.  A  leaf 
of  purple  cabbage  answers  the  same  purpose.  Acids 
color  it  red,  while  potash,  and  the  alkalies,  change 
the  red  to  green. 

325.  EFFECT  OF  HEAT  TO  PRODUCE  COM- 

What  is  the  . 

effect  of  heat       BINATION. It    IS    86611  from  the    foregoing, 

on  chemical       ^^  h    t  j       ft       essential   to   chemical 

combination  ? 

combination.  This  is  almost  always  the 
case  where  both  substances  are  solid.  Beside  height- 
ening their  chemical  affinity,  heat  has  the  effect  of 
bringing  the  particles  into  closer  and  more  general  con- 
tact, and,  within  the  range  of  affinity,  by  the  melting 

*Litmus  is  a  blue  vegetable  pigment  much  used  by  chemists,  for  the 
purpose  mentioned  in  the  text. 


138  LAWS    OF    COMBINATION. 

or  fusion  which  it  accomplishes.  Sulphur  and  iron,  for 
example,  require  the  aid  of  heat  to  bring  about  their 
union.  The  sulphur  melts,  and  then  combines  with 
the  iron. 

326.  Further  heating,  has  often  just  the 

Mention  an-  ~,  ,  , 

other  effect  of  contrary  enect.  it  causes  substances  al- 
heat.  ready  combined,  to  separate  from  each  other 

again.  This  is  especially  the  case,  when  one  of 
them  is  a  gas.  Thus,  if  oxide  of  silver  or  gold  is 
heated,  the  oxygen  passes  off  in  the  gaseous  form,  and 
leaves  the  metal  behind. 

327.  Heat  owes  its  decomposing  effect, 

Why  does  heat     .        ,  .  _      .      .. 

have  this  ef-      m  this  and  similar  cases,  to  the  tendency 


which  it  imparts  to  certain  substances,  to 
assume  the  gaseous  form.  And  as  all  bodies  would, 
probably,  be  gaseous,  at  a  sufficiently  high  tempera- 
ture, sufficient  heat  would  probably  decompose  all 
chemical  compounds. 

328.  EFFECT  OF   SOLUTION.  —  The  solu- 

What  is  the 

effect  of  solu-  tion  of  one  or  both  of  two  substances  to  be 
combined,  has,  in  a  multitude  of  cases, 
the  same  effect,  in  promoting  chemical  combination, 
as  that  produced  by  heat.  The  reason  is  also  the 
same.  It  brings  them  into  more  general  and  thorough 
contact.  This  is  illustrated  in  the  case  of  ordinary  soda 
powders,  the  two  constituents  of  which,  will  not  act 
on  each  other,  unless  one,  at  least,  is  dissolved. 

329.   ELECTRICAL    RELATIONS    OF   ELE- 

What  are  the 

electrical  rela-  MENTs.  —  1  he  metals  are  sometimes  spoken 
°^  as  electro~P°sitive  an(l  tne  metalloids  as 
electro-negative,  for  reasons  given  in  the 


ELECTRICAL  RELATIONS.  139 

chapter  on  galvanism.  Electricity  also  resolves  salts 
into  the  bases  and  acids  which  compose  them.  The 
acid  goes  to  the  positive  pole,  and  is,  therefore,  elec- 
tro-negative. The  base  goes  to  the  negative  pole,  and 
is,  therefore,  electro-positive.* 

*  The  laws  of  combination,  and  other  subjects  which  belong  to 
chemical  philosophy,  are  further  considered  in  the  chapter  on  Salts, 
in  the  introduction  to  Organic  Chemistry,  and  in  the  Appendix.  Ad- 
ditional remarks  on  the  atomic  theory  adopted  in  the  text,  are  also 
given  in  the  Appendix. 


141 


III. 


INORGANIC  CHEMISTRY. 


CHAPTER   I. 


What  is  oxy- 
gen 


METALLOIDS. 
OXYGEN. 

329.  DESCRIPTION.  —  Oxygen  is  a  trans- 
parent  and  colorless  gas,  a  little  heavier  than 
the  atmosphere.  It  is  much  the  most 
abundant  substance  in  nature.  One  fourth 

of  the  air,  one-ninth  of  the  ocean,  and,  probably,  half 

of  the  solid  earth,  is  oxygen. 
330  .  PREPAR- 
ATION. —  Gase- 

ous oxygen  is  expelled  from 

many    substances,     which 

contain    it,  by  the    simple 

agency  of  heat,     Chlorate 

of  potassa,  and  black  oxide 

of    manganese,    are     such 

substances. 

Give  the  com-        331.  Mix  equal  quantities  of  these  ma- 

phte  process,     terials,  and  heat  half  a  tea-spoonful  of  the 


How  is  oxygen 
prepared  ? 


142  METALLOIDS. 

dry  mixture  in  a  test-tube,  connected,  air-tight,  with  two 
clay  pipes,  as  represented  in  the  figure.  The  connec- 
tions are  made  by  winding  the  pipe-stems  with  strips 
of  wet  paper,  folded  in  such  a  manner  that  the  stopper 
thus  formed  tapers  slightly  toward  the  end.  The  first 
portions  of  gas,  which  contain  an  admixture  of  the  air  of 
the  tube,  are  allowed  to  bubble  through  the  water,  and 
escape.  The  rest  is  made  to  rise  into  a  half-pint  vial, 
which  it  gradually  fills,  by  displacing  the  water.  The 
vial  has  previously  been  filled  with  water,  then 
covered  with  a  bit  of  glass,  inverted  in  the  wa- 
ter. If  it  is  desired  to  hang  it  on  the  side  of  the 
bowl,  a  hook  is  then  introduced,  made  of  strong, 
doubled  wire,  the  two  parts  being  kept  about  half 
an  inch  apart,  and  the  vial  is  then  hung,  by  its  help,  on 
the  side  of  the  bowl ;  or  this  may  be  dispensed  with, 
and  the  vial  held  by  the  hand  in  its  proper  place,  while 
the  gas  is  collected.  When  the  process  is  completed, 
vial  and  hook,  if  the  latter  has  been  used,  are  to  be  low- 
ered into  the  bowl,  the  mouth  being  carefully  kept 
below  the  surface  ;  the  hook  is  then  removed,  the  mouth 
covered  with  a  bit  of  glass,  and  the  vial  then  inverted 
upon  a  plate  containing  a  little  water,  and  so  kept  until 
it  is  wanted  for  an  experiment.  All  other  gases,  that 
are  not  absorbed  by  water,  may  be  collected  in  the 
same  manner. 

Explain  the  332.    EXPLANATION. — Although   black 

process.  oxide  of  manganese  may  be  employed  as 

a  source  of  oxygen,  it  does  not  yield  this  gas  at  the 
temperature  employed  in  the  above  experiment.     But, 


OXYGEN.  143 

for  reasons  not  well  understood,  the  admixture  of  this 
or  any  other  infusible  powder,  facilitates  the  evolution 
of  this  gas  from  the  chlorate.  At  a  red  heat,  part  of 
the  double  portion  of  oxygen  which  the  black  oxide 
contains  is  expelled  in  a  gaseous  form. 

332.  A  SIMPLER  METHOD. — The  above 

Give  a,  simpler 

method  of  pre-    method,  for    preparing    oxygen,    is    here 

paring  oxygen     ^^    becauge    it  iUustrates    the    mode     of 

collection  of  gases  in  large 
quantities,  and  makes  its 
accumulation  visible  to  the 
eye.  The  oxygen  needed 
for  the  following  experi- 
ments will  be  more  con- 
veniently prepared  by  pla- 
cing the  mouth  of  the  test-tube,  containing  the  proper 
materials,  in  a  wide-mouthed  vial,  and  heating,  as  be- 
fore. As  the  gas  is  evolved,  it  will  expel  the  air,  and 
soon  fill  the  vial. 

333.  IRON  BURNED  IN  OXYGEN. — Make 

How  cm  iron 

be  burned  in  a  coil  of  very  fine  iron  wire,  by  winding 
the  latter  around  a  pencil ;  fasten  one  end 
into  the  middle  of  a  cork,  by  slitting  the  lat- 
ter, and  attach  a  fine  splinter  to  the  other  end. 
Light  the  splinter,  and  introduce  it  into  a  vial 
of  oxygen.  The  wire  itself  will  take  fire, 
and  burn  with  brilliant  scintillations.  In  this 
and  the  following  experiments,  the  cork  is  to 
be  placed  loosely  over  the  mouth  of  the  vial,  to  pre- 
vent its  violent  expulsion  by  the  heated  gas. 


144  METALLOIDS. 

334.  EXPLANATION.— In  this  experiment 

What  takes  .   ,  .  .  .        - 

place  in  the       the  oxygen    in   the  vial   unites  with  the 

"nenir^™'       *r°n    °^    tn6    WirG'    and  becomes    soli(i,    in 

the  form  of  oxide  of  iron.  The  oxide 
fuses  into  a  small  globule  on  the  end  of  the  wire,  and 
occasionally  falls,  and  melts  its  way  into  the  glass. 
This  is  apt  to  be  the  case,  even  when  water  is  left  in 
the  bottom,  so  that  a  vial  is  likely  to  be  destroyed  by 
this  experiment.  The  process  is  exactly  the  reverse  of 
that  which  takes  place  when  binoxide  of  manganese  is 
heated,  to  produce  oxygen.  In  the  one  case,  oxygen 
was  driven  from  the  metal ;  in  the  other,  it  is  drawn 
to  it,  though  not  in  the  same  proportion. 

335.  TAPER  REKINDLED  IN  OXYGEN. — 

Describe  the 

taper  experi-  Introduce  a  newly  extinguished  taper,  or 
shaving,  which  has  a  little  fire  on  the  wick, 
into  a  vial  of  oxygen.  It  will  be  immediately  rekin- 
dled. This  experiment  may  be  many  times  repeated 
without  a  new  supply  of  gas. 

336.  Combustion    is    more    vivid    in 

Explain  t/te 

last  experi-       pure  oxygen,  than  in  air,  because  the  latter 
is  diluted  with  other  gases,  which  do  not 
take  part  in  the  combustion. 

337.  COMBUSTION    OF     PHOSPHORUS. — 

Describe  the  . 

experiment        Place  a  piece  of  phosphorus,  of  the 

with  phosphor     gize  of  a  pea?  on  a  piece  of  chdkj 

slightly  hollowed  out  for  the  pur- 
pose, and  connected  with  a  cork  by  a  fine 
wire.  Ignite  the  phosphorus,  and  introduce 
it  immediately  into  a  bottle  of  oxygen.  It 


OXYGEN.  145 

will  burn  with  the  utmost  brilliancy,  producing  a  light 
which  the  eye  can  scarcely  bear. 

338.     The  white  fumes  which  fill  the 

VFha  t  acid  re- 
sults from  this    bottle  in  this  experiment,  are  composed  of 

experiment?  particies  of  phosphoric  acid,  which  are 
produced  by  the  union  of  the  phosphorus  and  oxy- 
gen. They  collect  on  the  sides  of  the  vial,  and  soon 
dissolve  in  water,  which  they  absorb  from  the  air. 
The  water  will  be  found  to  possess  a  sour  taste,  and 
to  redden  blue  litmus  paper,  which  is  a  characteristic 
of  acids. 

339.  COMBUSTION  OF  CHARCOAL. — At- 

Descnbe  the 

experiment        tach  a  small  piece  of  charcoal  to 

with  charcoal?     &    fine    wire,    ignite  Qne    end  of  ^ 

thoroughly,  and  introduce  it  into  a  vial  of  ox- 
ygen, having  a  cork  at  the  other  end,  as 
before.  It  burns  with  brilliant  sparks.  A  piece 
of  charcoal  bark  is  best  adapted  to  this  pur- 
pose. 

340.  Carbonic  acid  is  formed   in    the 

What  is  pro- 
duced in  this  above  experiment,  from  the  union  of 
experiment  ?  carbon  with  oxygen.  It  is  a  gaseous  acid, 
and  cannot  be  seen.  Neither  can  it  be  detected  by 
its  taste.  But  a  piece  of  moistened  litmus  paper,  held 
for  some  time  in  the  bottle,  will  be  reddened  by  it,  and 
proof  of  the  presence  of  an  acid  may  be  thus  obtained. 
When  wood  burns,  it  also  yields  carbonic  acid. 

341.  DEFINITION  OF  COMBUSTION. — All 

Dciine  com-  /.   ,,  ,  .  /. 

bustion.  °f  tne    above  experiments    are  cases   of 

combustion,  and  combustion  may  be  den- 
ned as  combination  of  any  two  substances,  attended  by 

7 


146  METALLOIDS. 

light  and  heat.  Metals  which  will  not  burn  in  the 
air,  because  it  is  diluted  oxygen,  burn  brilliantly,  as 
has  been  seen,  in  pure  oxygen. 

342.  PREVIOUS  HEAT  REQUIRED.  —  In  or- 

Why  is  heat         _  _ 

required  to  der  that  most  substances  may  burn,  they 
Uon/°mbHS'  must  first  be  heated>  to  increase  their  affin- 
ity for  oxygen.  Take  carbon,  as  an  exam- 
ple. Before  heating,  its  affinity  for  oxygen  is  not  suf- 
ficient to  bring  about  the  requisite  combustion.  In  this 
condition  it  may,  therefore,  lie  for  any  length  of  time, 
in  the  air,  or  oxygen  gas,  without  uniting  with  it. 
But  heat  stimulates  the  tendency  to  combination,  and 
the  bit  of  charcoal  previously  ignited,  goes  on  burning, 
until  it  is  consumed.  The  first  particles  obtain  the 
necessary  stimulus  of  heat,  from  the  previous  igni- 
tion, the  next  from  the  burning  of  the  first,  and  so  on. 

343.  UNCOMBINED  OXYGEN  REQUISITE.  —  • 
What  kind  of     __  '. 

oxygen  is  re-  Mere  presence  of  oxygen  is  not  sufficient 
amlnrtion?  for.  combustion.  It  must  be  free,  or  un- 
combined  oxygen.  After  burning  char- 
choal  in  oxygen  gas,  the  vial  contains  just  as  much 
oxygen  as  before,  but  being  already  combined,  it  has 
no  affinity,  or  appetite,  for  more  carbon,  and  there- 
fore will  not  produce  a  new  combustion. 

344.  EACH  PARTICLE  IN  TURN  MUST  BE, 

If  each  parti- 

cle is  not  heat-    HEATED.  —  If  the   first  particles  that  com- 


bme'  do  llot  communicate  sufficient  heat 
to  the  next,  then  the  combustion  stops. 
This  may  be  illustrated  by  lighting  a  tightly  wound 
roll  of  paper,  and  holding  the  flame  upward.  It  is 
soon  extinguished,  because  the  heat  that  is  produced 


OXYGEN.  147 

by  the  combustion  of  one  portion  of  the  paper,  is  not 
communicated  to  the  next,  but  passes  off  into  the  air. 
But  if  the  taper  be  held  with  the  flame  downward, 
each  particle  in  turn  receives  the  stimulus  of  heat  ne- 
cessary to  combination,  and  the  whole  is  consumed. 

345.  DECAY  OF    LEAVES    AND    WOOD. — 

What  causes 

the  decay  of  The  decay  of  leaves  and  wood,  is  a  sort 
of  slow  combustion,  but  not  sufficiently 
vigorous  to  produce  light  and  heat.  In  this  case,  as  in 
the  ordinary  combustion  of  wood  or  coal,  the  particles 
which  have  combined  with  oxygen,  pass  off  into  the 
air,  in  an  invisible  form. 

346.  BLEACHING. — Bleaching  may  also 

How  may  .  * 

bleaching  be      be  regarded  as  a  kind  of  slow  combustion. 
On  exposing  cloth  to  sun  and  air,  its  color- 
ing matter  is  gradually  burned  up,  by  the  atmospheric 
oxygen. 

347.  OXYGEN  A  PURVEYOR  TOR  PLANTS. 
oxygen\»  a°     ^  nas  been  seen  that  both  in  combustion 
purveyor  for      an(j  decaVj  the  oxygen  of  the  air  combines 

with  the  particles  of  leaves,  and  wood,  and 
coal,  and  passes  off  with  them  in  an  invisible  form.  It 
flies  off  with  them  into  the  air,  and  yields  them  again 
to  living  plants,  to  produce  new  leaves  and  flowers,  and 
fruits.  Indeed,  they  are  entirely  dependent,  for  their 
support,  on  what  they  thus  obtain  from  the  death  and 
decay  of  their  predecessors,  through  the  agency  of  this 
ever  active  purveyor,  the  oxygen  of  the  air.  But  for 
the  fact  that  the  particles  of  vegetable  and  animal  mat- 
ter, can  thus  be  used  again  and  again,  the  supply  would 


148  METALLOIDS. 

soon  be  exhausted,  and  vegetation  cease  upon  the  face 
of  the  earth. 

348.  OZONE. — By  passing  an  electrical 
How  is  °*°ne  current,  continually,  through  oxygen  gas, 
for  some  time,  it  becomes  mysteriously 
changed  in  its  proportions.  In  this  changed  condition 
it  is  called  ozone.  It  is,  as  it  were,  intensified  in  its  affin- 
ities by  the  current,  so  that  like  chlorine,  it  will  attack 
silver,  and  exhibit  many  other  of  the  properties  of  the 
latter  gas.  The  electricity  of  the  air  has  similar  effects 
on  the  oxygen  which  it  contains,  and,  in  consequence  of 
its  varying  electrical  condition,  the  proportion  of  ozone 
is,  also,  from  time  to  time,  extremely  varied.  There  is 
reason  to  believe  that  this  substance  has  important  influ- 
ence upon  health,  and  that  either  its  deficiency  or  excess, 
is  injurious.  In  cholera  seasons,  it  has  been  observed 
to  be  present  in  comparatively  small  quantity,  while, 
during  the  prevalence  of  a  species  of  influenza  called 
"  grippe,"  it  is  said  to  be  more  abundant.  These  obser- 
vations need  confirmation,  by  further  experiments,  before 
the  facts  can  be  regarded  as  fully  established.  The  pres- 
ence of  ozone,  is  indicated  by  the  discoloration,  through 
the  influence  of  a  current  of  air,  of  a  test  paper,  de- 
scribed in  the  section  on  chlorides. 
Tir,  349.  RELATIONS  TO  LIFE. — Oxygen  is 

What  relation 

to  life  does  ox-    as  essential  to  life,  as  it  is  to  combustion. 

ygen  sustain!     The    ^^    oxygen  of    the    ^    ig    better 

adapted  to  breathing,  than  pure  air,  but  that  which  con- 
tains much  less  than  its  due  proportion,  is  no  longer 
fitted  to  support  life.  Respiration  consumes  oxygen,  so 
that  the  air  of  a  close  room  is  constantly  being  depri- 


CHLORINE.  149 

ved  of  this  essential  constituent,  without  obtaining  any 
new  supply.  As  a  consequence,  it  soon  becomes  unfit 
to  breathe.  The  case  is  similar  to  that  of  a  taper 
burned  in  a  bottle.  The  oxygen  of  the  air  in  the  bot- 
tle, is  gradually  consumed,  and  the  flame  grows  grad- 
ually more  and  more  dim,  till  it  goes  out.  So  life  grows 
fainter  and  fainter,  in  a  close,  unventilated  room. 
What  is  said  350.  Oxygen  has  been  used,  with  great 
of  oxygen  as  success,  as  a  means  of  resuscitation,  in  cases 

a  means  of  ' 

resuscitation  ?  of  suffocatio.ii  and  drowning,  when  similar 
use  of  air  was  without  effect.  In  such  cases,  it  is  forced 
into  the  lungs  through  a  tube,  from  a  jar  or  bladder. 

CHLORINE. 

What  is  chlo-  351.  DESCRIPTION. — Chlorine  is  a  yel- 
TwLreisit  lowish  green  gas,  of  peculiar  odor,  about 
found"!  %\  times  as  heavy  as  the  air.  More  than 

one  half  of  common  salt  is  chlorine.     Salt  mines  and 
the  ocean,   therefore,  contain  it  in  immense  quantities. 
352.  PREPARATION. — Chlo- 

How  is  chlo- 

rineprepar-  nne  is  prepared  from  muriat- 
ic acid,  which  is  composed  of, 
chlorine  and  hydrogen,  by  using  some 
agent  to  retain  the  latter,  and  liberate  the 
former.  Black  oxide  of  manganese  is1 
such  a  substance. 

Give  the  com-  353.  The  oxide  is  well  covered  with  mu- 
picte  proceeds.  rjatic  acid,  and  kept  warm,  as  the  evolution 
of  the  gas  proceeds.  This  is  best  effected  by  a  cup  of 
hot  water,  as  represented  in  the  figure.  Chlorine  gas 
soon  displaces  the  air  in  the  second  vial.  It  should  be 
corked  as  soon  as  filled. 


150  METALLOIDS. 

Explain  the  354.  It   will  be  remembered   that  black 

process.  oxide   of  manganese,   is  a  substance  con- 

taining a  double  portion  of  oxygen,  part  of  which 
is  feebly  held,  and  very  willing  to  go.  Its  use  in 
making  chlorine,  depends  on  this  fact.  The  loosely 
held  oxygen,  seizes  upon  the  hydrogen  of  the  muri- 
atic acid,  remaining  with  it  as  water,  and  at  the  same 
time  setting  its  chlorine  at  liberty. 

355.  A  SIMPLER  METHOD. — Acids  expel 

Describe  an-  .          -  ,  ,  .   ,        , 

other  method  chlorine  from  many  bases  which  have 
of  preparing  previously  been  made  to  absorb  it. 

chlorine  f 

Lime  is  one  of  these  bases.  Bring 
into  a  wide-mouthed,  half-pint  vial,  a  table 
spoonful  of  dilute  sulphuric  acid,  and  add 
rather  more  than  the  same  bulk  of  chlo- 
ride of  lime,  or  bleaching  powder.  It  is  best 
to  add  it  in  small  portions,  covering  the  vial 
with  a  cork  or  bit  of  glass,  after  each  addition. 
The  vial  will  soon  be  filled  with  faintly  green  chlorine 
gas.  More  of  the  materials  will  be  required,  if  the 
chloride  of  lime  is  deteriorated  by  exposure  to  the  air, 
as  is  often  the  case.  The  gas  thus  produced,  may  be 
used  for  most  of  the  experiments  which  follow,  with- 
out transferring  it  to  another  vessel. 

356.  CHLORINE,  HEAVIER  THAN 
that  chlorine     AIR. — This  is  already  imperfectly 
lhan *a£f         Proved;  in  the  first  method  of  col- 
lecting chlorine,  but  the   follow- 
ing proof  is  more  satisfactory.     The  gas  pro- 
duced in  the  last  experiment,   may  be  slowly 
poured 'from   the  vessel    containing    it,    into 


CHLORINE.  151 

another  wide-mouthed  vial.  The  second  vial,  if 
the  smaller  of  the  two,  may  be  thus  filled  without  re- 
ceiving any  acid  from  the  first.  In  small  quantities 
the  gas  cannot  be  seen  to  flow,  but  will  actually  pass 
from  one  vessel  into  the  other.  Its  presence  may  be 
proved  by  the  methods  given  in  the  following  experi- 
ments. 

357.   CHLORINE  DISSOLVES  IN  WATER.  — 
that  chlorine     Having  filled  a  vial  with  chlorine,  by  the 


" 


first  of  the  methods  above  described,  cork  it, 
and  open  it  under  water,   contained  in  a 

bowl.  As  the  gas  dissolves  in  the  water, 

the  latter  will  rise  to  take  its  place.  When 

it  has  risen  a  little  way,  cork,  and  shake 

the   vial,  and  open  it  again  below  the 

surface.     The   water  will  then  rise  and 

dissolve  still  more  of  this  gas.     The  so- 

lution is  to  be  set  aside  for  a  subsequent  experiment. 

Gas  produced  by  the  second  method  above  described, 

may  also  be    used  in  this  experiment,    if  previously 

transferred  to  another  vial. 

358.  ACTION  OF  CHLORINE  ON  METALS. 

Describe  the 

action  of  chlo-  Chlorine  gas  combines  with  many  metals, 
rine  on  metals.  convertmg  tnem  into  chlorides.  Their  ac- 

tion may  be  illustrated  by  sprinkling,  finely  pulverized 
antimony,  into  a  bottle  of  chlorine.  Each  particle  of 
metal  ignites  as  it  falls  through  the  gas,  and  a  minia- 
ture shower  of  fire  is  thus  produced.  The  white  smoke 
which  is  produced  in  this  experiment,  is  composed  of 
minute  particles  of  chloride  of  antimony. 


152  METALLOIDS. 

359.  NASCENT  CHLORINE. — Nascent  chlo- 

What  ts  the  . 

action  of  nas-  rme,  in  its  action  on  the  metals,  is  the  most 
cent  chlorine*  powerful  agent  known.  Even  the  noble 

metals  yield  to  its  power,  and  waste  away  in  the  liquid 
which  contains  it.  The  term  nascent  signifies  being 
born,  or  in  the  act  of  formation. 

What  is  the  360<    A11  §ases  are   most  energetic,  in 

general  fact      their  action  at  the   first  moment  of  their 

in  relation  to  . 

nascent  bo-  separation  from  compounds  which  contain 
them,  and  while  they  may  be  regarded  as 
still  retaining  the  solid  form  themselves.  The  subse- 
quent expansion  into  the  gaseous  form,  diminishes  their 
energy. 

36.1.  Nascent  chlorine  is  best  obtained 

How  is  nas-  ..  ,        *  i      •          •  i        •  i    i     i  /»    . 

cent  chlorine     by  mixing  hydrochloric  acid  with  half  its 

best  obtained?    bujk  of  strong    nitr[c    aci(j.       guch  a    mix_ 

ture  is  called  aqua  regia.  The  latter  acid  compels  the 
former  to  yield  a  constant  supply  of  its  own  chlorine  in 
the  nascent  condition.  It  does  this,  by  means  of  its  oxy- 
gen, which  seizes  upon  the  hydrogen  of  the  hydrochlo- 
rine  acid,  forming  water,  and  sets  its  chlorine  at  liberty. 
The  remnant  of  the  nitric  acid  escapes,  as  in  the  case 
of  its  action  on  metals  hereafter  described. 

362.     CHLORINE  DECOMPOSES  WATER. — 

Does  chlorine  . 

decompose  wa-  11  chlorine  water  be  exposed  to  the  sun 
for  some  days,  it  loses  its  green  color. 
The  chlorine  combines  with  the  hy- 
drogen of  the  water,  forming  hydro- 
chloric acid,  and  sets  its  oxygen  at 
liberty.  If  the  experiment  be  made  in 
a  bottle,  inverted  in  water,  so  that  the 


CHLORINE.  153 

oxygen  may  collect,  bubbles  of  this  gas  will  be  found 
above  the  liquid.  This  experiment  proves  the  pow- 
erful affinity  of  chlorine  for  hydrogen. 

363.  BLEACHING  BY  CHLORINE. — Intro- 

How  is  calico  _ 

bleached  by  duce  bits  of  calico  into  the  solution  01 
chlorine  ?  chlorine  before  obtained.  Most  colors  will 
soon  disappear.  If  the  solution  is  weak,  the  bleaching 
effect  will  be  better  shown,  with  infusion  of  litmus  or 
red  cabbage.  Color  may  also  be  removed  from  cloth 
or  paper  by  hanging  the  article  to  be  bleached,  pre- 
viously moistened  with  water,  in  a  vial  of  gaseous 
chlorine. 

364.  Chlorine  water  may  be    prepared 

How  ts  chlo- 
rine water  best    in   larger  quantity,  by  leading  the   gas  di- 

preparcd?  rectiy  jnto  water.  The  first  of  the  two 
methods  before  described,  will  be  found  the  most  ad- 
vantageous. 

365.     OXYGEN   THE    REAL   BLEACHING 

Explain  how 

chlorine  AGENT. — The  real  bleaching  agent  in  this 

bleaches.  method  of  bleaching,  is  the  same  as  that 

mentioned  in  paragraph  346.  It  is  oxygen,  always 
present  during  the  process,  as  an  element  of  the  water 
which  moistens  the  material.  The  chlorine  simply 
acts  to  bring  nascent  oxygen  into  activity.  It  does 
this  by  depriving  it  of  the  hydrogen  with  which 
it  is  combined.  The  oxygen  having  thus  lost  its  com- 
panion, looks  about,  as  it  were,  for  something  else 
with  which  to  combine.  The  coloring  matter  of  the 
cloth  being  the  first  thing  at  hand,  is  destroyed  by  the 
extreme  energy  of  its  affinity. 
7* 


METALLOIDS. 

366.  ACTION  OF  NASCENT  OXYGEN. — The 

Show  the  ad- 
vantage of  superior  force  of  an  element  in  its  nascent 
nascent  oxy-  con(jition  js  strikingly  shewn  in  the  above 
experiment.  A  piece  of  calico,  hung 
in  a  bottle  of  oxygen  gas,  would  not  lose  its  color. 
But  the  nascent  oxygen  which  chlorine  liberates,  be- 
gins to  destroy  the  coloring  matter  on  the  first  instant 
of  its  liberation. 

367.  CHLORINE  AND  TURPENTINE. — Im- 

JJescnoe  the 

inflaming  of  merse  a  rag  wet  with  camphene  or  spirits 
of  turpentine  in  a  vial  of  chlorine 
gas.  It  is  immediately  inflamed, 
with  the  production  of  dense  black  smoke. 
Spirits  of  turpentine  is  composed  of  hydro- 
gen and  carbon.  The  former  combines 
energetically  with  chlorine,  as  to  produce 
flame  in  the  above  experiment,  while  the  latter 
is  separated  in  the  form  of  black  particles,  which  con- 
stitute the  smoke. 

368.  USE  AS  A  DISINFECTANT. — As  chlo- 

Is  chlorine  a 

disinfectant  ?  rine  destroys  color,  when  used  as  a  bleach- 
ing agent,  so  it  destroys  noxious  vapors  in 
the  air.  Its  minute  atoms  fly  forth  like  birds  of  prey, 
seizing  on  the  impurities  of  the  atmosphere,  and  de- 
vouring them.  Chloride  of  lime  is  commonly  substi- 
tuted for  chlorine  for  this  use.  A  little  of  this  salt  is 
placed  in  a  saucer,  and  moistened,  when  it  gradually 
yields  chlorine  through  the  action  of  the  carbonic  acid 
of  the  air.  Stronger  acids  evolve  it  abundantly. 


CHLORINE.  155 

369.  CHLORINE  A  DESTRUCTIVE  AGENT. 

What  is  said  .  . 

of  chlorine  as    Chlorine,  as  has  been  seen,  is  one  of  the 
a  destructive      mogt  destructive  of  all  substances.     It  not 

agent  £ 

only  destroys  colors  and  odors,  but  any 
kind  of  vegetable  or  animal  matter,  long  submitted  to 
its  action,  wastes  away,  and  is  destroyed.  It  does  this 
partly  by  its  own  direct  action,  and  partly  by  letting 
loose  the  atoms  of  nascent  oxygen,  as  before  described. 

370.  IN    WHAT    SENSE    DESTRUCTIVE. It 

In  what  sense 

is  it  destruct-  is  always  to  be  borne  in  mind  that  the 
term  destruction  is  used  in  chemistry  in  an 
entirely  figurative  sense.  Thus,  neither  oxygen  nor 
chlorine,  strictly  speaking,  destroy.  They  only  com- 
bine with  the  particles  of  the  substances  they  seem  to 
destroy,  forming  new,  and  often  invisible  compounds. 
Many  of  these  will  be  hereafter  mentioned. 

371.  RELATIONS  TO  ANIMAL  LIFE. — Chlo- 

G-ive  the  rcla-       .        . 

tions  of  Mo-    rine  is  a  poisonous  gas.     No  danger,  how- 
rmcto  animal   ever?  ig  to  be  apprehended  from  the  escape 

of  small  portions  into  the  air,  during  the 
preceding  experiments.  The  diluted  gas,  however,  is 
apt  to  produce  irritation  of  the  throat,  and  consequent 
coughing, 

In  what  re-  372.       RESEMBLANCE      TO     OXYGEN. In 

chTorinTre  many  respects  chlorine  is  similar  to  oxy- 
semble  oxy-  gen,  as  has  already  been  shown.  It  com- 
bines with  almost  all  of  the  elements,  and 
with  many  compounds.  This  combination  is  often 
attended  with  light  and  heat,  and  is  therefore  com- 
bustion. The  metal  antimony,  for  example,  as  has 


166  METTALLOIDS. 

already  been  shown,  will  burn,  in  chlorine  gas,  even 
without  kindling. 

Mention  some  373.    COMPOUNDS  OF   CHLORINE  AND  OXY- 

compounds  of    GEN  —  Chlorine  combines  with  five  atoms 

chlorine  and 

oxygen-  of  oxygen  to  form  chloric  acid.     This  acid 

is  of  importance,  principally,  as  a  constituent  of  the 
chlorate  of  potash,  to  be  hereafter  mentioned  in  con- 
nection with  Nitrates.  Hypoclorous  acid  a  constitu- 
ent of  bleaching  powders  is  another  compound  of  chlo- 
rine with  oxygen.  It  is  again  mentioned  in  the  section 
on  Chlorides. 

IODINE. 

v/ 
374.  DESCRIPTION.  —  Iodine  is  commonly 

dine?  WJiere  seen  in  the  form  of  brilliant  blue-black 
is  it  found?  scales,  somewhat  similar  to  plumbago  in 
appearance.  In  odor  it  resembles  chlorine.  It  is  found 
in  the  water  of  the  ocean,  in  sea-weeds,  sponges,  &c., 
but  always  in  combination  with  sodium,  or  some 
other  metal.  Minute  traces  of  it  are  found  to  exist  in 
the  atmosphere,  and  thence  are  transferred  to  the  bodies 
of  animals. 

375.  PREPARATION.  —  For  the  preparation 

Explain  the  .       . 

manufacture     oi  iodine,  a  lye 

of  iodine?  made  fj.om  the 


ashes  of  certain  sea-weeds, 
is  heated  with  oil  of  vitriol 
and  black  oxide  of  manga- 
nese. The  liberated  oxy- 
gen of  the  latter  expels  va- 


IODINE.  157 

pors  of  iodine  from  the  mixture.  These  being  led  into 
a  receiver,  crystallize  in  brilliant  scales.  A  retort  and 
receiver  are  commonly  used  in  the  process.  The  ashes 
of  sea- weed,  employed  for  the  purpose,  are  called  kelp, 
and  are  prepared  in  great  quantities  on  the  coast  of 
Scotland. 

VIOLET  VAPORS  or  IODINE. 


violetlapors      Introduce  a  few  scales  of  iodine  into 
of  iodine  pro-    a  test-tube  or  vial,  and  heat  it  for 

duced? 

a  moment  over  the  spirit  lamp.  The 
solid  iodine  is  immediately  converted  into  a 
beautiful  violet  vapor,  which  fills  the  vial.  As 
the  latter  cools,  the  iodine  becomes  again  solid, 
in  the  form  of  minute  crystals.  On  warming 
these  crystals,  thejeolbr  re-appears. 

^^077.  COLORING    EFFECT  ON    STARCH. - 

Describe  the        jjeat    a    |juie    iO(Jme    in    a    ^ive 
effect  produ- 
ced by  iodine     stem,  and  as  soon  as  vapors  ap- 

°paste?C  pear,  blow  them  against  a  sheet 

of  paper,  covered  with  figures 
made  with  thin  starch  paste.  The  iodine  vapor  imme- 
diately colors  them  blue.  The  paste  may  be  made  in 
a  test-tube,  over  a  spirit  lamp. 

378.   ENGRAVINGS  COPIED  BY   IODINE.- — 

How  are  en- 
gravings copi-  A  transient  copy  of  an  engraving,  or  other 
ed  by  iodine  ?  prmtecj  matter,  may  be  made,  by  exposing 
it  to  faint  fumes  of  iodine,  and  then  pressing  it  down 
upon  paper  moistened  with  vinegar,  or  dilute  nitric 
acid.  The  vapors,  adhere  to  the  ink  only,  and  are 
transferred  by  pressure ;  producing,  with  the  starch 
contained  in  ordinary  letter  paper,  a  blue  impression. 


158  METTALLOIDS. 


BROMIDE. 

379.  Bromine  is  a  dense  reddish-brown 
of  bromine?  fluid,  exhaling  at  ordinary  temperatures,  a 
deep  orange-colored  vapor.  It  is  similar,  in 
its  chemical  properties,  to  chlorine,  but  the  latter  is 
the  stronger  of  the  two,  and  expels  bromine  from  its 
compounds.  Thus,  if  chlorine  be  passed  into  one  end 
of  a  heated  tube  containing  bromide  of  silver,  the  va- 
pors of  bromine  will  be  seen  to  pass  out  at  the  other 
end,  and  escape,  while  the  chlorine  remains,  and  takes 
possession  of  the  metal.  Bromine,  like  chlorine,  is 
found  in  sea- water,  and  in  the  water  of  mineral  springs, 
combined  with  sodium,  or  some  other  metal.  The 
power  of  chlorine  to  expel  it  from  its  compounds,  is 
made  use  of  in  manufacturing  bromine.  This  sub- 
stance is  used  in  photography,  but  is  otherwise  of  little 
general  interest.  Although  widely  distributed,  it  ex- 
ists in  nature,  in  comparatively  small  quantities.  Bro- 
mine vapors  have  the  effect  of  imparting  to  starch  a 
beautiful  orange  color. 

FLUORINE. 

'^What  is  said  380.  Fluorine  is  yellowish-brown  gas, 
of  fluorine?  Of  strong  odor,  somewhat  similar  to  that  of 
chlorine.  It  is  one  of  the  elements  of  the  beautiful 
mineral,  fluor  spar.  It  is  prepared  from  the  fluoride  of 
potassium,  by  means  of  the  galvanic  current.  Its  isola- 
tion has  been  attended  with  great  difficulties,  and  the 


SULPHUR.  159 

gas  is  therefore  imperfectly  known.  Its  principal  com- 
pounds, are  hydrofluoric  acid,  and  fluor  spar,  to  be  here- 
after described.* 

S.ULPHUR. 

381.  DESCRIPTION. — Sulphur  is  a  brittle 

W/iatissul- 

phur?  Where  yellow  solid,  burning  with  a  peculiar  odor, 
it  occur?  ma(je  familiar  in  the  ignition  of  common 
friction  matches.  With  the  metals,  it  forms  sulphides 
or  sulphurets.  In  Sicily,  and  certain  other  volcanic 
regions,  it  occurs  in  beautiful,  yellow  crystals.  Gyp- 
sum, and  iron  pyrites,  or  fools  gold,  represent  the  two 
principal  classes  of  minerals  that  contain  it.  It  also 
enters  in  small  proportion  into  the  composition  of  all 
animal  and  vegetable  substances.  It  is  the  sulphur  in 
eggs  that  blackens  the  silver  spoon  with  which  they  are 
eaten. 

382.  PREPARATION. — In  preparing  com- 

Describe  the 

manufacture  mercial  sulphur,  the  impure  material  of 
of  suphur  ?  voicanic  regions,  is  highly  heated,  and  thus 
made  to  fly  off  as  vapor,  leaving  its  earthy  impurities 
behind.  The  vapors  are  condensed  as  flowers  of 
sulphur.  The  process  by  which  a  solid  is  thus  vap- 
orized, and  re-converted  into  a  solid,  is  called  sublima- 
tion. Native  sulphur  may  also  be  partially  purified  by 
simple  fusion.  Its  earthy  impurities  having  settled, 
it  is  poured  off  into  moulds,  and  thus  converted  into 
roll  brimstone. 

*  Many  compounds  of  chlorine,  bromine,  iodine  and  fluorine,  with 
each  other  and  with  oxygen,  are  known  to  the  chemist,/but  they  are 
without  interest  to  the  general  student 

V 


160  METTALLOIDS. 

383.  SUBLIMATION  OF  SULPHUR. — 
SlZlf     The  sublimation  of  sulphur  may  be 

of  sulphur  be    shown  by  heating  a  small  bit  of  the     \ 

shown  ? 

substance  in  a  test-tube.  Flowers 
of  sulphur  will  deposit  in  the  upper  portion  of 
the  tube. 

384.  COMBUSTION    OF    SULPHUR.- 

What  is  said       ,__  .  . 

of  the  com-       Melt  some  flowers    of  sulphur  upon 

^afphur°{  the     6nd    °f    a    wire     wound     with 

thread,  and  hang  them  after  ignition  in  a 
vial  of  oxygen  gas.  The  oxygen  gas  com- 
bines with  the  sulphur,  forming  a  new  com- 
pound gas,  called  sulphurous  acid.  A  bril- 
liant blue  flame  accompanies  the  combina- 
tion. It  thus  appears  that  acids  may  be  gase- 
ous, as  well  as  liquid.  The  acidity  may  be 
proved,  as  usual,  by  blue  litmus  paper. 

385.  BLEACHING   BY  SULPHUR. — Intro- 

Descnbe  the 

process  of  duce  a  red  rose,  or  other  flower,  into  a  vial 
mTansnofbL.  filled  with  sulphurous  acid.  It  will  soon 
phur  ?  lose  its  color.  Wash  it  with  dilute  sulphu- 

ric acid,  and  the  color  re-appears  This  experiment 
may  also  be  made  in  a  bottle,  in  which  sulphur  has 
been  burned  in  common  air. 

386.     EXPLANATION. — Sulphurous   acid 

Why  docs  sul-  -,       •  ,      ,  ,       , 

phurous  acid  lorms  a  white  compound  with  the  red  color- 
bieach?  -ng  matter  Of  the  rose  ft  mav  seem  incom- 

prehensible, that  a  colorless  gas,  and  red  coloring 
matter  should  unite  to  form  white,  and  it  would  be 
so,  were  the  case  one  of  mere  mixture.  But  it  is  an 


SULPHUR.  161 

instance  of  chemical  combination,  in  which  as  is  often 
the  case  the  properties  of  the  constituents  entirely  /dis- 
appear. When  sulphuric  acid  is  afterward  used,  the  co- 
lor re-appears,  because  the  stronger  acid  has  expelled 
the  weaker,  and  has  itself  no  inclination  to  form  with 
the  coloring  matter  a  similar  combination. 

387.  STRAW    BLEACHING. — The  bleach- 
proccL  If ie      m£  °f  straw  goods  is  always  effected  by 
straw  bleach-     sulphurous  acid.    They  are  first  moistened, 

and  then  exposed  to  the  fumes  of  burning 
sulphur.  An  inverted  barrel  is  often  made  to  serve 
the  purpose  of  a  bleaching  chamber.  Articles  thus 
bleached  by  sulphurous  acid,  after  a  time,  regain  their 
color.  This  is  not  the  case  in  chlorine  bleaching,  be- 
cause the  coloring  matter  is  not  merely  changed,  but 
destroyed.  The  agent  is  not  applicable  to  straw,  on 
account  of  a  faint  brown  tinge  which  it  imparts  to  the 
material. 

388.  COPYING    MEDAL- 
?        LIONS.  —  Sulphur    melts, 


medallions  by   readily,   by  application  of 

sulphur?  *\          ,  :*. 

heat.  At  a  higher  temper- 
ature, it  thickens  again.  Still  further 
heating,  makes  it  again  fluid.  In 
this  second  period  of  fluidity,  it  has  the  remarkable 
property  of  assuming  a  waxy  consistence,  on  being 
poured  into  water.  In  this  condition,  it  is  used  for 
copying  seals,  coins,  and  medals.  The  copy  acquires, 
in  a  few  hours,  the  original  hardness  of  sulphur.  The 
plastic  material  may  be  obtained  in  the  form  of  elastic 


162  METTALLOIDS. 

strings,  by  pouring  molten  sulphur  from  a  test-tube, 
into  cold  water. 

389.  SULPHUR  CRYSTALS. — Sulphur  may 

How  may  crys- 

talsof  sul-  be  obtained  in  a  crystalline  form,  by  melt- 
*tained?°  *n£  ^  *n  a  P^P6  bowl,  at  a  gentle  heat,  and 

then  allowing  it  to  cool.     A  crust 
soon  forms  on  the  top,  which  is  broken,  and  a 
portion  of  the  liquid  sulphur  below,  poured  out. 
On  breaking  the  pipe,  it.  is  found  filled  with  crystals, 
shooting  across  the  interior,  from  the  encrusted  walls. 

SULPHURIC  ACID. 

Describe  sul-  390.  DESCRIPTION. — Sulphuric  acid  is  a 
phuric  acid.  colorless,  oily  fluid,  of  intensely  acid  taste, 
known  in  commerce  as  oil  of  vitriol.  It  is  composed 
of  sulphur  and  oxygen,  in  the  proportion  of  one  atom 
of  the  former,  to  three  of  the  latter.  It  also  contains 
Water,  with  which  it  is  chemically  combined.  As 
it  is  among  the  most  important  of  all  chemical 
products,  the  process  of  its  manufacture  will  be  given 
with  some  detail. 

391.  PREPARATION. — Sulphuric  acid  may 

How  may  sul-  .  . 

phuric  acid  be  be  made  directly,  from  its  elements,  by  ig- 
prepai  nithig  a  mixture  of  air  and  vapor  of  sul- 

phur, with  a  red-hot  'iron.  In  quantity,  it  is  always 
made  from  sulphurous  acid,  by  imparting  to  the  latter 
additional  oxygen.  Take  a  bottle  in  which  sulphur 
has  been  burned,  and  which,  therefore,  contains  sulphur- 
ous acid,  and  hold  in  it,  for  a  short  time,  a  rod  or  stick 


,„. 

SULPHURIC    ACID.  163 

moistened  with  nitric  acid.  The  gaseous  sulphurous 
acid  obtains  oxygen  from  the  nitric  acid,  which  is  rich 
in  this  element,  and  very  liberal  of  it,  and  thereby  be- 
comes sulphuric  acid.  A  little  water,  previously  placed 
in  the  bottom  of  the  vial,  absorbs  the  acid 
thus  formed.  To  acidify  the  water  to  any 
considerable  extent,  it  will  be  necessary  to 
burn  sulphur,  and  introduce  the  moistened  rod 
repeatedly.  That  the  acid  is  not  the  sulphu- 
rous or  the  nitric  acid,  employed  in  the  pro- 
cess, may  be  proved  by  using  it  to  make  hy- 
drogen gas. 

392.    REMARK. — The  red  fumes  which 

What  causes  . 

the  red  fumes     nil  the  vial  m  the  last  experiment,  consist 


of  the  changed  nitric  acid,  (nitric  oxide,) 
which  has  just  given  up  part  of  its  oxy- 
gen, and  is  now  resuming  part  of  it  from  the  air.  It 
thereby  becomes  a  third  substance,  of  a  red  color,  to 
be  again  mentioned  in  the  section  on  nitric  acid. 

393.  MANUFACTURE  OF  OIL  OF  VITRIOL. 

Explain  how  . 

sulphuric  acid  — The  method  of  the  production  of  oil 
lurcd™^™  °^  vitri°l  on  a  large  scale,  is  essentially  the 
same  as  that  above  given.  Fumes  of 
burning  sulphur,  and  vapor  of  nitric  acid,  with  air  and 
steam,  are  introduced  into  a  leaden  chamber,  when  the 
process  proceeds,  as  before  described. 

394.  Comparatively  little  nitric  acid  is 

Why  is  but 

little  nitric  needed  in  the  process,  for  it  is  found  that 
acid  required  wnjje  ft  y^ids  oxygen  to  the  sulphurous 
fumes,  the  changed  acid  greedily  seizes  oxygen  from 
the  air  of  the  chamber,  arid  imparts  it  again,  to  keep  up 


164  METALLOIDS. 

the  process.  The  air  is,  therefore,  the  real  oxidizer, 
while  the  changed  nitric  acid  only  acts  to  transfer  it 
to  the  sulphurous  fumes. 

Describe  the  395.      DESCRIPTION    OF    ACID     CHAMBERS. 

acid  chambers,  rpne  fjgure  represents  one  form  of  the 
leaden  chambers 
employed  in  the 
above  manufac- 
ture. Connect- 
ed with  them 
are  a  steam  boiler  and  two  furnaces,  in  one  of  which 
sulphur  is  burned,  and  converted  into  sulphurous  acid. 
Over  the  sulphur  is  another  vessel,  containing  the 
materials  for  making  nitric  acid,  the  formation  of  which 
commences  as  soon  as  the  sulphur  flame  has  imparted 
the  requisite  heat.  The  vapors  thus  produced,  are 
mingled  with  air  and  steam  in  the  leaden  chamber. 
How  they  act  together  to  produce  sulphuric  acid,  has 
been  already  explained.  The  space  is  divided  by  a 
partition,  in  order  that  all  the  materials  may  be  more 
thoroughly  mixed,  as  they  pass  through  the  narrow 
opening  below  it.  The  acid,  as  it  forms,  dissolves  in 
water  which  covers  the  bottom  of  the  chamber,  and  is 
thus  collected.  Lead  is  used  as  a  lining  for  the  cham- 
bers, because  the  acid  woul-d  destroy  almost  any  other 
material  that  might  be  employed. 

396.  The  dilute  acid  obtained  from  the 

How  is  the 

chamber  acid     chambers,  is  concentrated  first  in   leaden 

concentrated?      vessels?  and  afterward)  when  it  hag  become 

strong  enough  to  corrode  the  lead,  in  retorts  of  platinum. 
The  metal  platinum,  being  of  about  half  the  value  of 


SULPHURIC    ACID.  165 

gold,  the  vessels  in  which  the  evaporation  is  carried 
on,  are  extremely  expensive.  Some  manufactories  de- 
liver tens  of  thousands  of  pounds  of  sulphuric  acid  per 
day. 

397.  COMPARATIVE    STRENGTH  OF   SUL- 

Hov)  is  the 

strength  of  PHURIC      ACID.  —  SulphUHC     acid      JS      the 

Sshmvn?iC  °cid  strongest  of  a11  acids-  This  ma7  be  shown 
by  bringing  it  to  a  direct 'trial  of  strength 
with  other  strong  acids.  If  poured,  for  example,  on 
nitrate  of  potassa,  which  is,  as  its  name  implies,  a  com- 
pound of  nitric  acid  and  potassa,  it  takes  sole  possession 
of  the  base,  and  expels  the  nitric  acid  in  the  form  of 
vapor.  It  expels  muriatic  acid  from  its  compounds  in 
the  same  manner.  This  is  the  method  by  which  nitric 
and  muriatic  acids  are  always  obtained.  Whatever 
they  can  accomplish  when  free,  may  therefore  be 
traced  back  to  the  power  of  sulphuric  acid,  which  gave 
them  their  liberty.  The  latter  is  the  king  among  the 
acids,  who  accomplishes  indirectly,  what  he  cannot  ef- 
fect in  person.  The  solution  of  the  noble  metals  by 
aqua  regia  is  one  among  these  indirect  results. 

398.  Sulphuric  acid  is  volatile  at  high 

Is  it  strongest 

at  high  tenipe-  temperatures.  Phosphoric,  and  other  non- 
volatile acids,  are,  therefore,  under  certain 
circumstances,  superior  to  it.  This  is  illustrated  in  cer- 
tain crucible  operations,  where  compounds  containing 
sulphuric  acid  are  heated  with  such  acids.  The  sul- 
phuric acid  is  then  easily  dispossessed,  and  compelled 
to  take  refuge  in  flight. 

What  is  the  399.        ACTION     OF      SULPHURIC    ACID    ON 

action  of  sul-    METALS.— Sulphuric  acid  attacks  all  metals, 

jjliunc    acid 

on  metals.          with  the  exception   of  platinum  and  gold. 


166  METALLOIDS. 

Even  the  dilute  acid  acts  on  all  the  metals  hereafter 
named,  as  far  as  manganese. 

400.  The  action  of  the  dilute  acid  may 

Illustrate  the  .  . 

action  of  the  be  illustrated,  by  placing  a  few  bits  of  zinc 
dilute  acid.  in  a  tumbler?  with  a  iittie  waterj  and  ad- 
ding a  small  portion  of  oil  of  vitriol.  The  metal  dis- 
solves with  the  evolution  of  hydrogen  gas.  The  rea- 
son of  the  evolution  of  this  gas  has  been  already 
given. 

401.  The  action  of  the  strong  acid  may 

Illustrate  the  J 

action  of  the  be  illustrated,  by  heating  a  little  copper, 
strong  acid.  w{ih  Q[{  of  vitriol>  in  a  test-tube.  The 

metal  dissolves  with  the  evolution  of  sulphurous  acid 
fumes.  The  reason  of  the  appearance  of  sulphurous 
acid  will  be  given  in  the  next  section. 

402.  AFFINITY  FOR  WATER. — The  affin- 
liffinlt  °*ofwl-    ity  °f  sulphuric  acid  for  water  is  so  strong 
phurtc  add       that  it  lays  hold   on  every  particle  of  the 

for  water?  .  /   f  , 

invisible  aqueous  vapor  of  the  atmosphere. 
It  finds  it,  in  what  seems  the  driest  air  ;  and  every  par- 
ticle which  it  catches,  it  retains.  It  grows  in  bulk 
by  what  it  thus  drinks,  as  will  be  seen  if  a  little  oil  of 
vitriol  is  left  exposed  to  the  air,  for  a  few  days,  in  an 
open  vessel.  It  is  sometimes  necessary,  in  chemical 
operations,  to  free  gases  from  all  the  aqueous  vapor 
which  is  mixed  with  them.  This  is  done  completely, 
by  causing  them  to  bubble  through  oil  of  vitriol,  and 
again  collecting  them. 

403.    HEAT  BY  DILUTION. — When   sul- 

What  takes  . 

place  whensui-    phuric  acid  and  water  are  mixed,  conden- 
U    sati°n  ta^es  place,  accompanied  by  eleva- 
tion of  temperature.     Fiftv  cubic  inches  of 


SULPHUROUS     ACID.  167 

sulphuric  acid,  and  fifty  cubic  inches  of  water,  when 
mixed,  do  not  fill  a  vessel  of  the  capacity  of  one  hun- 
dred cubic  inches,  but  fall  about  three  inches  short. 
Condensation  has,  therefore,  taken  place  to  the  amount 
of  three  inches.  Heat  is,  as  it  were,  pressed  out  in 
such  cases,  as  explained  in  the  early  part  of  this  work. 

404.       WOOD      CHARRED      BY      SULPHURIC 

Why  does  sul- 
phuric acid       ACID. — Wood    dipped   in    oil   of  vitriol    is 

soon  charred.  Wood  is  composed  of  car- 
bon, hydrogen,  and  oxygen.  The  last  two  together 
form  water.  The  affinity  of  sulphuric  acid  for  water  has 
been  mentioned  above.  The  acid  and  the  wood  being 
in  contact,  it  would  seem  that  the  hydrogen  and  the 
oxygen  of  the  latter  agree  to  combine  and  satisfy  this 
demand.  The  carbon  being  at  the  same  time  isolated, 
appears  in  its  natural  black  color.  Sulphuric  acid  ex- 
erts a  similar  action  on  other  vegetable  substances. 

405.    IMPORTANT  USES. — Sulphuric  acid 

What  are  the  . 

uses  of  sul-  is  largely  employed  for  dissolving  indigo, 
pkuric add?  for  use  in  dyeing  and  calico  printing  .  aiso? 

for  converting  common  salt  into  sulphate  of  soda,  as  a 
preparatory  step  to  the  manufacture  of  carbonate  of 
soda.  It  is  also  essential  in  the  manufacture  of  super- 
phosphate of  lime,  an  article  now  so  extensively  used 
in  agriculture.  Nitric  and  muriatic  acids  are  pro- 
duced through  its  agency  from  nitre  and  common 
salt. 

SULPHUROUS  ACID. 

What  is  sul-  406.  DESCRIPTION. — Sulphurous  acid  is 
phurous  acid?  a  gaSj  having  the  smell  of  a  burning  match. 


168 


METALLOIDS. 


It  is  composed  of  sulphur  and  oxygen,  in  the  proportion 
of  one  atom  of  the  former  to  two  of  the  latter.  The  ter- 
mination "  ous"  indicates,  as  in  other  cases,  a  smaller 
proportion  of  oxygen  than  is  contained  in  some  other 
acid  composed  of  the  same  elements. 

407.  PREPARATION. — It  has  already  been 

How  is  sul- 
phurous acid  shown  that  this  acid  may  be  prepared,  by 
prepared?  burning  sulphur  in  oxygen.  Another,  and 
better  method,  is  to  heat,  oil  of  vitriol,  with  bits  of  cop- 
per. The  oil  of  vitriol  is  thus 
deprived  of  part  of  its  oxygen, 
and  converted  into  sulphurous 
acid.  The  process  may  be  con- 
ducted in  a  test-tube.  By  lead- 
ing the  gas  through  a  smaller 
tube,  into  a  vial  partly  filled  with 
water,  a  solution  of  sulphurous 
acid  may  be  obtained,  possessed  of  the  same  bleaching 
and  other  properties  as  the  gas  itself.  When  the  evolu- 
tion of  the  gas  commences,  the  heat  of  the  lamp  is  no 
longer  required. 

Explain  the  408.  EXPLANATION. — Copper  has  a  very 

process.  strong   affinity  for   oxygen,   and   takes  it 

from  the  oil  of  vitriol,  which  possesses  it  in  large  pro- 
portion. The  oil  of  vitriol,  thus  deprived  of  part  of 
its  oxygen,  is  converted  into  sulphurous  acid  gas. 

409.      USE    IN    PRESERVING    WINES. Slll- 

W ny  ^.?  sul- 
phurous acid     phurous  acid,  in  small  quantities,  is  some- 

7eTtowlnesd?     times  added  to  wine>  to  prevent  its  sour- 
ing.    This  change  is  owing  to  the  absorp- 
tion of  oxygen  from  the  air.     Sulphurous  acid  is  a 


NITROGEN.  169 

substance  possessed  of  an  excessive  appetite,  or  affinity, 
for  oxygen.  A  small  portion  of  it  in  a  wine  cask,  will 
seize  on  what  little  oxygen  finds  admission,  and  so 
prevent  the  deterioration  of  the  wine.  It  destroys  it- 
self in  this  act  of  protection,  and  is  converted  into  sul- 
puric  acid. 

How  is  sul-  ^®'     ^SE    1N    SUGAR    MANUFACTURING. 

phurous  acid     The    oxygen  of  the  air  so   modifies  the 

employed  in         .    .  ~   ,,  ..     .    .  ,  , 

manufactur-  juice  of  the  sugar-cane,  that  it  cannot  be 
ing  sugar  ?  made  to  yield  its  due  proportion  of  sugar. 
Sulphurous  acid,  by  appropriating  the  oxygen  to  itself, 
prevents  this  effect,  and  is  said  to  double  the  product. 
It  is  generally  used  in  the  form  of  its  lime  compound, 
called  sulphite  of  lime.  The  objection  to  its  use  con- 
sists in  the  slight  sulphurous  taste  which  it  imparts  to 
the  sugar.  But  this  is  said  to  be  removed  by  clarifi- 
cation, at  a  loss  of  ten  per  cent.,  leaving  still  a  large 
gain  from  the  employment  of  the  process.  The  bleach- 
ing effects  of  sulphurous  acid  have  already  been  illus- 
trated. 

NITROGEN. 

411.  DESCRIPTION. — Nitrogen  is  a  trans- 
trogen  ?  parent  gas,  without  taste  or  odor.     It  forms 

Where  is  it      about  four_fifths  of  the  air  we  breathe.     It 

found  ? 

occurs  also  in  combination  with  other  ele- 
ments in  a  solid  form.  One-fifth  of  the  weight  of  the 
dried  flesh  of  animals  is  nitrogen.  It  also  enters  into 
the  composition  of  nitre  and  other  salts. 


170  METALLOIDS. 


Howisnitro-  ^-  PREPARATION.—  Nitrogen  is  pre- 
gen  prepared?  pared  from  ordinary  air  by  removing  its 
oxygen.  For  this  purpose  a  small  portion  of  phospho- 
rus is  floated  on  a  slice  of  cork  upon  water,  and  then 
kindled,  and  a  vial  inverted  over  it. 
As  it  burns,  it  abstracts  the  oxygen  ; 
the  water  rises  to  take  its  place,  and 
what  is  left  of  the  air  is  nitrogen. 
The  cork  should  be  a  little  hol- 
lowed out,  and  chalk  scraped  into 
the  cavity.  Water  must  be  poured  into  the  saucer  as 
the  first  portion  rises  into  the  bottle.  The  bottle  is 
then  cooled,  either  by  water  or  long  standing,  and 
co-rked  while  yet  inverted  It  is  then  shaken,  to  wash 
the  gas.  A  piece  of  phosphorus,  of  the  size  of  a  large 
pea,  is  sufficient  for  the  preparation  of  half  a  pint  of 
gas. 

Explain  the  413.  EXPLANATION.  —  The  burning  phos- 

process.  phorus  selects  all  of  the  oxygen  atoms  in 

the  air,  and,  by  combining  with  them,  converts  them 
into  solid  particles  of  a  certain  oxide  of  phosphorus, 
called  phosphoric  acid.  These  particles  at  first  ap- 
pear as  a  white  smoke,  and  are  afterward  dissolved  in 
the  water. 

414.  NITROGEN  EXTINGUISHES  FLAME.  —  If 

Does  nitrogen 

extinguish  a  burning  taper  be  lowered  into  the  bottle  of 
flame?  y.  njtrOgenj  as  above  prepared,  it  will  be  im- 
mediately extinguished.  Flame  is  the  brightness  which 
accompanies  active  chemical  combination,  but  here  is 
nothing  to  combine.  Nitrogen  is  a  sloth  among  the 
elements,  possessing  no  degree  of  chemical  activity. 


THE   ATMOSPHERE.  171 

415.  PRINCIPAL  OFFICE  OF  NITROGEN.—- 


What  is  the 


principal  of-  The  principal  office  of  the  nitrogen  of  the 
ficeofnitro-  air  is  to  dilute  its  oxygen.  The  latter,  if 
pure,  would  soon  consume  our  bodies,  as 
it  hastens  the  combustion  of  a  taper,  or  other  combus- 
tible. 

416.  THE  ATMOSPHERE. — The    air  we 

What  is  the 

composition  breathe,  and  which,  to  the  depth  of  fifty 
of  the  air?  miles  or  more;  forms  the  crystal  shell,  or 
envelope  of  the  globe  we  inhabit,  is  a  mixture  of  nitro- 
gen and  oxygen  gases,  with  aqueous  vapor.  It  also 
contains  small  and  varying  proportions  of  carbonic  acid, 
and  ammonia. 

417.  PROOF  THAT  AIR  is  A  MIXTURE. — 

How  is  it 

proved  to  be  a  That  it  is  a  mixture,  and  not  a  chemical 
compound,  is  sufficiently  evident  from  the 
fact  that  it  possesses  no  new  and  peculiar  properties 
different  from  those  of  its  constituents.  It  is  further 
proved  to  be  a  mixture,  from  the  fact  that  heat,  which 
is  the  usual  attendant  on  chemical  combination,  is  never 
occasioned  when  air  is  artificially  produced  by  the  ad- 
mixture of  its  constituents. 

yse  418.    USE  OF  CARBONIC  ACID  AND  AMMONIA 


served  by       IN  THE  AIR — Carbonic  acid  and  ammonia. 

its  carbonic 

acid  and  aw  although  present  in  the  air  in  extremely 
small  quantity,  subserve  the  most  impor- 
tant purposes  in  administering  to  the  growth  of  plants. 
They  constitute  the  gaseous  food  of  all  forms  of  vege- 
table life,  as  will  be  more  fully  explained  in  succeeding 
chapters  of  this  work. 


172  METALLOIDS. 

419.  ANALYSIS  OF  THE  AIR.  —  The  me- 

proportion  of  thod  bY  which  the  relative  amount  of  ox- 
nitrogen  deter-  ygen  and  nitrogen  in  the  air  is  determined 
has  been  already  given.  On  burning  phos- 
phorus under  a  glass  jar,  as  there  described,  the  water 
is  found  to  rise  and  fill  a 
little  more  than  one-fifth  of 
the  vessel,  thereby  indica- 
ting that  one-fifth  of  the 
air  which  it  contained  was 
oxygen  gas.  The  remaining  fths  is  nearly  all  nitro- 
gen. In  accurate  experiments,  a  graduated  tube  is 
employed,  instead  of  a  jar  or  tumbler.  It  is  not  es- 
sential that  the  phosphorus  should  be  ignited.  With- 
out ignition,  it  will  gradually  combine  with  all  the 
oxygen,  and  remove  it  from  the  air  contained  in  the 
tube. 

420.    In  order  to  determine  the  amount 

How  is  the  .       . 

amount  of  car-    of  aqueous  vapor  and  carbonic  acid  in  the 
atmosphere,  a   gallon,  or    other   measured 


nia  deter-          quantity  of  air,   is  drawn   through   tubes 

containing  materials  to  absorb  these   sub- 

stances.    This  quantity   is    known   by  the  increased 

weight  of  the  tubes  after  the  experiment  is  completed. 

421.  THE  APPARATUS  DESCRIBED.  —  The 

Describe  the  .  f. 

apparatus        apparatus  used  in  the  experiment  is  repre- 
wfedinthis       sented  in  the  last  figure.     It  consists  of  a 

analysis.  ° 

bottle,  or  small  cask,  filled  with  water,  and 
provided  with  a  cock  below.  The  cock  is  turned,  and 
as  the  water  no  ws  out,  air  flows  in  through  the  tube  to 
take  its  place.  The  quantity  of  air  that  has  passed 


NITRIC    ACID.  173 

through  the  tubes  is  known  by  the  quantity  of  water 
that  has  flowed  out  from  the  cask.  The  materials  em- 
ployed in  the  tubes  are  pumice  stone  drenched  with  oil 
of  vitriol,  in  the  first,  to  absorb  the  water ;  and  caus- 
tic potassa,  in  the  second,  to  retain  the  carbonic  acid. 
The  method  for  determining  the  amount  of  ammonia 
in  the  atmosphere  is  essentially  the  same,  muriatic  acid 
being  used  as  the  absorbant. 

422.     PROPORTIONAL    COMPOSITION    OF 

What  are  the 

proportions  of  THE  AIR. — The  proportions  of  the  four 
fousfttwnteof  constituents  of  the  air  above  mentioned, 
the  atmo-  as  obtained  by  the  method  just  described, 
are,  about  21  per  cent,  of  oxygen,  79  of 
nitrogen,  arWth  of  carbonic  acid,  and  t?4fofc¥rvtb  of 
ammonia.  The  proportion  of  aqueous  vapor  is  ex- 
tremely variable.  That  of  carbonic  acid  and  ammo- 
nia is  also  variable  to  a  considerable  extent. 


NITRIC  ACID. 

What  is  nitric  423.  DESCRIPTION. — Nitric  acid  is  a  thin. 
acid?  colorless,  and  intensely  acid  fluid.  It  cor- 

rodes metals  instantaneously,  with  the  evolution  of  deep 
red  vapor.  It  is  composed  of  nitrogen  and  oxygen,  in 
the  proportion  of  one  atom  of  the  former  to  five  of  the 
latter.  It  contains,  in  addition,  water,  with  which  it 
is  chemically  combined.  It  is  possible  to  make  it  an- 
hydrous, or  free  from  water,  but  such  an  acid  is  never 
used. 

How  is  nitric  424.  PREPARATION. — Nitric  acid  exists 
add  prepared?  m  a  dormant  state  in  ordinary  saltpetre. 


174  METALLOIDS. 

Its  affinities  being  entirely  satisfied  by  the  potassa  with 
which  it  is  combined  in  that  substance,  it  lies  there  per- 
fectly inactive.  Sulphuric  acid  being  stronger,  has  the 
power  of  taking  its  base, 
and  expelling  the  acid  in 
the  form  of  vapor.  In  or- 
der to  collect  and  condense 
the  acid  fumes,  the  mixture 
may  be  made  in  a  test-tube, 
the  mouth  of  which  opens 
into  a  vial  or  flask.  It  is  necessary  to  keep  the  vial 
covered  with  porous  paper  or  cloth,  and  to  moisten  it 
frequently  in  order  to  maintain  its  coolness.  Wher  e 
larger  quantities  are  prepared,  a  retort  and  well-cooled 
receiver  are  employed,  as  represented  in  the  Appendix. 
425.  OXIDATION  OF  METALS. — If  a  little 

What  effect 

has  nitric  acid  nitric  acid  is  poured  upon  a  copper  coin, 
placed  in  a  capsule  or  saucer,  the  coin  will 
immediately  begin  to  dissolve.  It  is  not,  strictly 
speaking,  the  metal  which  dissolves.  One  portion 
of  the  acid  first  converts  the  metal  into  oxide,  by  giving 
it  part  of  its  own  oxygen.  It  thereby  destroys  itself, 
while  another  portion  of  undecomposed  acid  dissolves 
the  oxide  which  is  formed.  One  portion,  in  reality, 
sacrifices  itself  to  satisfy  the  appetite  of  the  other.  Most 
other  metals  are  similarly  acted  on  by  nitric  acid. 
What  is  nitric  426.  NITRIC  OXIDE.* — The  vapors  which 
oxide?  are  gjven  off  m  the  jast  experiment  are 

*  It  will  be  observed  that  the  term  oxide  is  sometimes  applied  to 
compounds  of  the  metalloids  with  oxygen.  (See  chap,  iii.,  Inorg. 
Chem.) 


NITRIC    ACID.  175 

nitric  oxide,  changed  by  the  air  into  which  they  rise. 
The  nitric  oxide  is,  so  to  speak,  the  fragment  of  nitric 
acid,  which  is  left  after  three  atoms  of  its  oxygen  are 
abstracted.  Rising  into  the  air,  it  combines  with  oxy- 
gen enough  partly  to  supply  the  place  of  that  it  has 
just  lost,  and  is  thus  converted  into  red  fumes  of  per- 
oxide of  nitrogen,  containing  four  atoms  of  oxygen. 
This  compound  is  also  called  hyponitric  acid.  Still 
another  compound  of  nitrogen  with  oxygen  is  de- 
scribed in  the  section  on  nitrates. 

427.  Repeat  the  experiment  of  the  last 

JJeecrioe  ano-  .  •>--,• 

ther  method  of  paragraph,  placing  the  coin  and  acid  in  a 

rlddfum/s  Ule  sma11  vial  or  test-tube>  instead  of  a  saucer, 
and  collect  the  nitric  oxide  produced,  as 
shown  in  the  figure.  The  collec- 
tion should  not  be  commenced 
until  a  colorless  gas  is  produced. 
It  will  be  best  to  fill  the  vial 
to  only  two-thirds  of  its  capa- 
city. Then  lift  it  from  the 
bowl,  and  let  the  remaining  water  run  out.  The  air 
will  immediately  rush  in,  and  change  the  colorless  ni- 
tric oxide  to  red  vapors  of  the  peroxide  of  nitrogen. 

How  does  ni-  428.      OXIDATION    WITHOUT    SOLUTION. 

tnc  acid  act       Nitric  acid  oxidizes  tin  and  antimony,  but 

on  tin  {  J  ' 

does  not  dissolve  them.  The  experiment 
will  be  best  made  with  tin-foil.  After  the  action  of 
the  acid,  it  will  be  found  converted  into  a  white  pow- 
der. Gold  and  platinum  are  neither  dissolved  nor  ox- 
idized by  nitric  acid. 


176 


METALLOIDS. 


429.  COMBUSTION  BY  NITRIC  ACID. — As 

How  may  com- 
bustion be         nitric  acid  contains  much  oxygen,  combus- 
effectedby  ni-     j. jon  ^y  fa  means  would  seem  to  be  a 

probable  result.  To 
prove  that  it  has  this  effect,  boil 
strong  nitric  acid  in  a  test-tube, 
the  mouth  of  which  is  filled  with 
hair.  As  the  vapors  pass  through 
they  will  cause  it  to  smoke,  and, 
if  the  acid  is  sufficiently  strong, 
produce  ignition. 

430.  COMBUSTION     OF 

Describe  the  . 

experiment  Phosphorus  is  readily 
withphospho-  ignited  by  throwing  it 
upon  nitric  acid.  If 
the  acid  is  not  very  strong,  it  must  be  previously 
heated.  Particles  of  phosphorus,  scarcely  larger  than 
mustard  seed,  should  be  used  in  this  experiment. 


PHOSPHORUS.- 


Whatisphos 
phorus  ? 

Where  does  i 
occur? 


phosphate 
portion. 

flow  is  it  pre- 
pared ? 


PHOSPHORUS. 

431.     DESCRIPTION. — Phosphorus  is  a 
wax-like,  and  nearly  colorless,  solid,  read- 
t    ily  ignited  by  heat  or  friction.*1     It  forms 
part    of    the    mineral  apatite,  which  is  a 
of  lime.     Bones  also  contain  it  in  large  pro- 
It  is  never  found  umcombined. 

432.      PREPARATION. — Phosphorus     is 
made  from  bones.     These  are  composed, 


*  When  phosphorus  is  cut,  it  should  always  be  under  water,  and 
every  particle  not  used  should  be  immediately  returned  to  a  bottle 
containing  water. 


PHOSPHORUS.  177 

principally,  of  gelatine  and  phosphate  of  lime.  The 
individual  constituents  are  gelatine,  lime,  oxygen,  and 
phosphorus.  To  obtain  the  phosphorus,  all  the  rest 
are  to  be  first  removed.  Fire  removes  the  gelatine, 
oil  of  vitriol  the  lime,  and  charcoal,  the  oxygen. 
Give  the  com-  433.  The  bones,  having  been  previously 
piete  process,  burned,  the  ground  ash  is  mixed  with  di- 
lute sulphuric  acid  and  water,  and,  after  several  hours, 
filtered.  Sulphuric  acid  unites  with  the  lime,  forming 
an  insoluble  sulphate,  and  at  the  same  time  sets  the 
phosphoric  acid  at  liberty,  The  solution  containing 
phosphoric  acid  is  then  mixed  with 
charcoal,  and  heated  in  an  earthen 
or  iron  retort.  The  carbon  takes  the 
oxygen,  and  passes  out  of  the  retort  with  it, 
as  gaseous  carbonic  oxide.  The  phosphorus  which  is 
left,  being  vaporized  by  the  heat,  is  also  expelled,  but 
is  reconverted  into  solid  phosphorus  by  the  cold  water 
into  which  it  passes.  The  figure  will  give  some  idea 
of  the  arrangement.  The  neck  of  the  earthen  retort 
passes  into  a  copper  tube,  which  leads  into  water.  The 
gas  produced  by  the  process  bubbles  through  the  water 
and  escapes,  while  the  phosphorus  is  hardened  by  it, 
and  remains.  The  mass  thus  obtained  is  melted  under 
water,  and  run  into  moulds. 

434.  PHOSPHORESCENCE. — This  term  is 
phorescence°?~    applied  to  the  luminous  appearance  of  sea- 
water  when  agitated,  and  to  other  faint 
light,  unaccompanied  by  perceptible  heat.     It  is  ob- 
served when  an  ordinary  friction  match  is  rubbed  upon 

the  hand  in  the  dark.     The  light  is  owing  to  a  slow 

8* 


178  METALLOIDS. 

combustion  of  phosphorous,  which  takes  place  without 
kindling.  The  product  of  the  combustion,  is  a  white 
powder,  called  phosphorous  acid,  which  soon  becomes 
liquid,  by  absorbing  moisture  from  the  air. 

435.  A  HARMLESS  FIRE. — By  agitating 

How  may  a  . 

harmless  fire  phosphorus  with  ether,  a  small  portion  of 
be  produced  9  the  former  substance  is  dissolved.  This 
solution,  if  rubbed  upon  the  face  and  hands,  makes 
them  luminous,  in  the  dark.  This  is  another  case  of 
phosphorescence.  A  piece  of  phosphorous  of  the 
size  of  a  pea  is  amply  sufficient  for  the  experiment. 

436.  COMBUSTION  UNDER  WATER. — Phos- 
How  may 

phosphorus  be   phorus  may  be  burned  under  water,  by  the 

^te??™***  helP  of  substances  ricn  in  oxygen.  Chlo- 
rate of  potassa  is  such  a  substance.  Place 
a  few  scales  of  this  salt,  and  a  bit  of  phospho- 
rous of  the  size  of  a  pea,  at  the  bottom  of  a 
wine  glass  previously  filled  with  water.  Par- 
tially fill  the  bowl  of  a  pipe  with  oil  of  vitriol, 
and  drop  it  in  small  portions  on  the  mixture, 
bringing  the  pipe  stem,  each  time,  close  to  the  bottom 
of  the  glass.  As  soon  as  the  stronger  acid  is  applied, 
chloric  acid,  containing  much  oxygen,  is  liberated  and 
decomposed,  and  the  phosphorus  inflamed.  A  similar 
combustion  of  phosphorus,  by  means  of  nitric  acid, 
has  already  been  described. 

437.      FRICTION     MATCHES. — Ordinary 

What  is  said 

of  friction        phosphorus  is  too  inflammable  to   be  em- 
ployed in  the  manufacture  of  friction  match- 
es. By  heating  it  under  carbonic  acid  for  a  long  time,  it 
becomes  changed  in  color,  and  also  less  fusible  and  in- 


ARSENIC.  179 

flammable.     In  this  form  of  red  phosphorus,  it  is  used 
in  the  manufacture  of  friction  matches. 


ARSENIC. 
438.  DESCRIPTION. — Arsenic  is  a  grey 

Why  is  arsen-  /•  •  . 

ic introduced  substance,  of  metallic  lustre,  and  for  this 
metalloids?  reason,  commonly  classed  among  the  met- 
als. On  the  other  hand,  in  view  of  the 
compounds  which  it  forms,  and  especially  in  view  of 
the  fact  that  its  oxygen  compounds  are  acids,  and  not 
oxides,  it  is  more  properly  classed  among  the  metal- 
loids. Its  analogies  to  phosphorus  are  most  striking, 
and  it  is  for  this  reason  here  introduced,  in  immediate 
connection  with  that  element. 

In  what  re  •  439.    ANALOGIES    TO     PHOSPHORUS. Ar- 

spccts  do pkos-    sem'c  unites  with  oxygen  in  the  same  pro- 

phorus  and  .  J  ... 

arsenic  resem-  portions  as  phosphorus,  forming  similar 
acids.  These  in  turn  form  salts  resembling 
each  other  most  perfectly,  in  external  appearance  and 
in  crystalline  form.  It  also  combines  with  three  atoms 
of  hydrogen,  to  form  arseniuretted  hydrogen,  a  gas 
analogous  to  phosphuretted  hydrogen,  to  be  hereafter 
described.  Of  the  two  principal  oxygen  compounds  of 
phosphorus,  the  higher,  or  phosphoric  acid,  is  the  more 
important,  and  was  therefore  more  particularly  consid- 
ered. On  the  other  hand,  the  lower  orarsenious  acid,  is 
the  more  important  of  the  acids  of  arsenic. 
How  is  arsenic  440.  PREPARATION. — Metallic  arsenic  is 
prepared  ?  found  native.  It  may  also  be  prepared 


180  METALLOIDS. 

from  arsenious  acid,  by  heating  with  a 
large  proportion  of  carbon,  as  in  the 
Case  of  phosphorus,  before  described. 
Beside  mixing  with  carbon,  it  is  best, 
also,  to  cover  with  the  same  material, 
and  heat  from  above,  downwards.  The  metal  passes 
off  as  vapor,  and  condenses  in  the  cooler  part  of  the 
tube,  or  other  vessel  in  which  the  experiment  is  per- 
formed, as  a  steel  grey  incrustation. 

ARSENIOUS  ACID. 

441.    RATSBANE. — The   ordinary  white 

What  are  the  ,  J 

properties  of  arsenic  of  the  shops,  also  known  as  rats- 
arscnious  bane,  is  a  white  and  nearly  insoluble  sub- 
stance, possessed  of  a  slightly  sweetish 
taste.  It  is  not  properly  arsenic,  but  arsenious  acid.  It 
contains  three  atoms  of  oxygen,  to  one  of  metal.  Al- 
though sweet,  it  is  called  an  acid,  because  it  possesses 
the  chemical  characteristic  of  an  acid,  viz  :  the  ca- 
pacity of  uniting  with  bases  to  form  salts. 
Howisitpre-  442.  PREPARATION. — Arsenious  acid  is 
pared?  prepared  from  metallic  sulphurets,  many  of 

which  contain  a  certain  proportion  of  arsenic,  by 
roasting  in  the  air,  and  thus  burning  out  their  arsenic,  in 
the  form  of  arsenious  acid.  The  fumes  are  condensed 
in  high  chimneys,  from  which  the  incrustation  of  the 
solid  acid  is  afterward  removed.  Mispickel,  which  is 
a  double  sulphuret  of  iron  and  arsenic,  and  certain 
ores  of  nickel  and  cobalt,  are  much  employed  for  the 
production  of  arsenious  acid. 


ARSENIC.  181 

„„  443.  POISONOUS  PROPERTIES  OF  ARSENIC. 

What  is  said 

of  arsenic  as  White  arsenic  or  arsenious  acid  is  a  fearful 
a  poison?  poison,  and  more  frequently  employed  than 
any  other  substance,  for  the  destruction  of  life.  But 
its  detection,  and  the  entire  demonstration  of  its  pres- 
ence in  the  body,  after  death,  or  in  materials  which 
have  previously  been  ejected  from  the  stomach,  is  cer- 
tain. 

444.  No  one  but  a  professional  chemist 

What  is  said 

of  its  detec-  should  undertake  such  an  investigation, 
tijon  ?  involving,  as  it  does,  the  issues  of  life  and 

death.  No  one  else,  indeed,  can,  be  qualified  to  guard, 
with  certainty,  against  the  presence  of  arsenic  in  the 
chemicals  which  are  used  in  the  process,  or  in  other  res- 
pects, to  bring  the  inquiry  to  that  point  of  absolute  de- 
monstration, which  is  always  required  in  judicial  inves- 
tigations. But  the  methods  of  detection,  being  simple, 
and  a  subject  of  interesting  and  instructive  experiment 
to  the  student,  will  be  briefly  described  in  the  paragraphs 
which  follow.  Many  other  compounds  of  arsenic,  be- 
side arsenious  acid,  are  highly  poisonous. 

How  arsenic  i*  ^45.    DETECTION    OF   ARSENIC. If   a  few 

detected?  drops  of  a  solution  of  chloride  of  arsenic* 

be  added  to  the  liquid  from  which  hydrogen  is  being 
evolved  from  a  vial,  by  the  ordinary  process,  the 
nascent  hydrogen  decomposes  the  chloride  of  arsenic 
and  carries  off  the  metal,  in  the  form  of  a  gas.  On  sub- 
sequently kindling  the  hydrogen  jet,  and  bringing 


*  Such  a  solution  is  prepared,  by  dissolving  white  arsenic  in  hydro- 
chloric acid. 


182  METALLOIDS. 

down  upon  it  a  cold  white  surface,  like  that  of 
a  plate  or  saucer,  the  metal  is  again  given  up, 
and  reveals  itself  as  a  brownish  black  and  high- 
ly lustrous  stain.  The  process  may  be  con- 
ducted in  an  ordinary  vial,  to  which  a  pipe 
stem,  or  glass  tube  has  been  fitted,  by  the 
method  before  described.  The  above  method 
of  detection  is  called  Marsh's  test.  In  a  case  of 
suspected  murder  by  poison,  the  moment  of  the  in- 
troduction of  the  pure  porcelain  into  the  flame,  be- 
comes one  of  the  most  intense  interest.  The  gather- 
ing stain,  is  at  once  the  emblem  of  guilt  and  sentence 
of  ignominious  death. 

446.    EXPLANATION. — The    decomposi- 
Sxplainthe       tjon  Of  arsenious  ac{d  by  hydrogen,  in  the 

above  process.  J       J 

above  experiment,  and  the  reason  of  the 
deposition  of  the  metallic  mirror,  still  remains  to  be  ex- 
plained. The  nascent  hydrogen  affects  the  decompo- 
sition of  the  acid,  by  a  double  action  ;  on  the  one  hand 
uniting  with  the  metal  to  form  arseniuretted  hydrogen, 
which  escapes,  and  on  the  other  hand,  with  its  chlorine 
to  form  hydrochloric  acid,  which  remains  behind.  The 
mirror  of  metal  is  deposited  upon  the  plate  or  saucer, 
because  the  introduction  of  the  cold  body  into  the 
flame,  so  lowers  its  temperature  that  the  metal  itself  can- 
not burn.  If  the  jet  of  gas  is  left  to  burn  without  in- 
terference, both  of  its  constituents  are  consumed  to- 
gether, and  the  flame  assumes  a  blue  color,  from  the 
presence  of  the  arsenic. 


ARSENIC.  183 

How  are  ar-  '    DISTINCTION  BETWEEN  ARSENIC  AND 

tenicandan-  ANTIMONY  STAINS. — If  in  testing  for  arsen- 
Smguish™  ic>  by  the  method  above  described,  a  metallic 
cd-  spot  is  obtained,  the  evidence  of  the  pres- 

ence of  arsenic  is  not  entirely  conclusive.  A  solution 
of  antimony,  if  substituted  for  arsenic  in  the  experi- 
ment, will  give  rise  to  the  production  of  somewhat  sim- 
ilar stains.  But  the  experimenter  will  find,  on  com- 
paring the  two  kinds  of  spots,  that  they  are  of  quite 
different  appearance.  Those  of  antimony  are  of  deep- 
er black,  and  fainter  lustre.  Again,  those  of  arsenic 
are  much  more  readily  removed  by  heat.  "  Chloride  of 
soda,"  is  a  still  more  conclusive  means  of  distinguish- 
ing them.  A  solution  of  this  substance  will  dissolve 
the  arsenic  stains,  while  it  leaves  those  of  antimony 
unaffected.  The  "  chloride  of  soda,"  to  be  used  in 
the  experiment,  is  prepared  by  adding  an  excess  of  car- 
bonate of  soda,  to  a  solution  of  "  chloride  of  lime," 
and  then  filtering  the  liquid. 

448.  ADDITIONAL  TESTS  FOR  ARSENIC. — 

Mention  some  .         ..       , 

additional  A  second  test  has  already  been  given  in 
l^tcs/or  arse'  the  paragraph  on  the  preparation  of  me- 
tallic arsenic,  to  which  the  student  is  re- 
ferred. The  formation  of  a  yellow  precipitate,  on  the 
addition  of  hydro-sulphuric  acid  to  a  solution,  also 
renders  it  highly  probable  that  arsenic  is  present. 
If  on  drying  the  precipitate,  and  heating  it  with  a 
mixture  of  cyanide  of  potassium  and  carbonate  of  soda, 
a  metallic  mirror  is  obtained,  the  inference  of  the  pres- 
ence of  arsenic  is  confirmed.  The  process  is  to  be 
conducted  as  directed  in  paragraph  440.  In  this  exper- 


184 


METALLOIDS. 


iment,  the  cyanide  of  potassium  has  the  effect  of  retain- 
ing the  sulphur,  while  it  allows  the  volatile  arsenic  to 
pass  and  deposit  above. 

449.  Still  another  evidence  of  the  pres- 

What  is  said 

of  the  garlic  ence  of  arsenic,  is  afforded  in  the  charac- 
teristic garlic  odor  which  is  emitted  by  the 
flame  produced  by  burning  arsenic,  in  the  experi- 
ment previously  described,  called  Marsh's  test.  The 
same  odor  is  also  obtained  on  sprinkling  a  little  ar- 
senious  acid  upon  burning  charcoal. 

Mention  the  450.    PREPARATIONS    FOR    THE     ARSENIC 

preparations     TEST> — Before    proceeding   with  the   che- 

for  the  ar- 
senic test?  mical  experiments  for  the  detection  of  ar- 
senic, some  preliminary  labor  is  com- 
monly required,  to  bring  the  material  to 
be  tested  into  proper  form.  It  com- 
monly consists  of  matters  which  have 
been  ejected  from  the  stomach,  or  of  the 
contents  of  the  stomach  itself.  If  the 
student  wishes  to  begin  at  this  point,  in  his  experi- 
ments, he  may  add  a  small  portion  of  arsenic  to 
some  bread  and  water,  and  proceed  with  this  paste,  in 
his  investigation.  This  mixture  is  to  be  diluted  with 
water,  and  saturated  with  chlorine,  as  in  the  process  for 
preparing  a  solution  of  this  gas.  Chlorine  has  the  effect 
of  destroying  a  certain  portion  of  the  organic  matter, 
and  rendering  the  rest  floculent,  so  that  the  liquid  may 
be  easily  separated  from  it  by  filtration.  It  also  brings 
the  arsenic  perfectly  into  solution,  as  a  chloride.  This 
solution  is  then  filtered,  and  treated  as  directed  in  the 
preceding  paragraphs. 


CARBON.  185 

What  is  the  ^^*    ANTIDOTE    TO    ARSENIC. The    hy- 

antidotefor  drated  sesquoxide  of  iron  is  regarded  as 
the  best  antidote  to  arsenic.  (See  Oxides.) 
Its  action  depends  on  the  formation  of  a  compound, 
with  the  poison  in  the  stomach,  which  is  insoluble, 
and  therefore  inactive.  Milk,  sugar,  and  white  of  eggs, 
are  also  given  with  advantage,  as  in  most  other  cases 
of  poisoning. 

452.    ARSENIC  EATERS  OF   AUSTRIA. — 

What  is  said      _         .  .  .,     . 

of  the  arsenic  In  the  mountainous  portions  of  Austria, 
triar?°^AuS~  bordering  on  Hungary,  the  peasantry  are 
„  given  to  the  strange  habit  of  eating  arse- 
nic. It  is  said  to  impart  a  fresh,  healthy  appearance  to 
the  skin,  and  also  to  make  respiration  freer  when  as- 
cending mountains.  Those  who  indulge  in  its  use 
commence  with  half  a  grain,  and  gradually  increase 
the  dose  to  four  grains.  If  this  habit  is  regularly  in- 
dulged, its  injurious  effects  are  said  to  be  long  retarded. 
But  as  soon  as  the  dose  is  suspended,  the  symptoms  of 
poisoning  by  arsenic  immediately  manifest  themselves. 

CARBON. 
453.  DESCRIPTION. — Carbon  in  the  form 

Describe  the  . 

different  of   coal,   is   a    black,   brittle,    solid.      As 

forms  of  car-  piumDago,  and  coke,  it  is  grey,  with  me- 
tallic lustre  ;  as  the  diamond,  it  is  trans- 
parent, and  the  hardest  of  known  substan- 
ces. Plumbago  is  commonly  called  black 
lead,  but  it  contains  no  lead  whatever.  The 
figure  in  the  margin  represents  the  more 
common  crystalline  form  of  the  diamond. 


186  METALLOIDS. 

454.  OCCURRENCE. — In  the  form  of  bi- 
carbon  occur?    tuminous  and  anthracite  coals,  carbon  ex- 
ists in  immense   quantities,  buried  in  the 

earth,  in  various  countries ;  as  graphite,  or  plumbago, 
it  is  also  quite  a  common  mineral  ;  as  the  diamond,  it 
is  the  rarest  of  all  gems.  It  is  one  of  the  elements  in 
limestones,  marbles  and  chalk,  which  are  all  carbonate 
of  lime.  It  forms  nearly  one  half  of  all  dried  veget- 
able matter,  and  more  than  half  of  all  dried  animal 
matter.  One  two-thousandth  of  the  air,  also,  is  car- 
bonic acid,  of  which  carbon  is  a  constituent. 

455.  CHARCOAL.— The 

Illustrate  the 

preparation      preparation  of  charcoal,  one 

of  charcoal.         Qf  the  forms  Qf  carboilj  may 

be  illustrated  by  heating  a  small  por- 
tion of  wood  or  cork,  in  a  test-tube. 
The  other  constituents  of  the  wood, 
and  part  of  the  carbon,  are  converted 
into  water,  gases,  and  tan,  and  the  larg- 
est part  of  the  carbon  ramains  behind,  in  the  form  of 
charcoal. 

456.  PREPARATION. — In  quantity,  it  is 
coal  made?  commonly  made  by  burning  wood  in  large 
heaps,  previously  covered  with  earth  and 
sod.  It  is  necessary  to  admit  a  little  air,  through  open- 
ings in  the  heap,  to  maintain  a  partial  combustion. 
If  too  much  air  is  admitted,  the  wood  is  entirely 
consumed,  and  no  charcoal  is  produced.  Coke  is 
made  from  bituminous  coal,  by  a  similar  process,  and 
is  also  obtained  as  a  residue  in  the  manufacture  of 
coal  gas. 


CARBON.  187 

457.  LAMP  BLACK. — Lamp  black,  still  an- 
other  form  of  carbon,  is  made  by  conducting 
the  smoke  of  rosiri  into  chambers,  construct- 
ed for  the  purpose.     It  consists  of  unburned  particles  of 
carbon.      It  is    used,   extensively,   in   making   paint. 
Bone  black  is  made  by  heating  bones  in  closed  vessels. 
It  is  a  sort  of  charcoal  produced  from  the  gelatine  of 
the  bones. 

458.  PURIFYING  PROPERTIES  OF  CHAR- 

Dcscribe  the 

purifying          COAL. — Charcoal  absorbs  gases,  and  retains 

ZtoalS°f  them  iri  its  Pores'  in  lar§e  qualities. 
Tainted  meat,  and  musty  grain,  intimately 
mixed  with  it,  become  sweet.  The  charcoal  has  re- 
moved the  unpleasant  gases,  proceeding  from  them. 
The  absorbent  power  of  charcoal  may  be  illustrated, 
by  holding  a  paper  moistened  with  ammonia,  in  a  vial, 
until  the  air  within  it  has  acquired  a  strong  ammo- 
niacal  odor.  On  afterward  introducing  some  pow- 
dered charcoal,  and  shaking  the  vial,  the  odor  will  be 

removed. 

459.  PRESERVATIVE     PROPERTIES     OF 

Illustrate  the  ,  , 

preservative       CHARCOAL. — Charcoal   may  be  used   as  a 
properties  of     preventive,   as  well  as  a  corrective   of  de- 

charcoal f 

cay.  Posts,  if  charred  at  the  bottom,  be- 
fore they  are  set,  are  rendered  more  durable.  Water 
will  keep  longer  in  charred  vessels  than  in  those  which 
have  not  thus  been  prepared.  The  decay  of  meats  and 
vegetables  is  retarded  by  packing  them  in  charcoal. 
Charcoal  is  itself,  one  of  the  most  unchangeable  of  sub- 
stances. Wheat  and  rye  charred  at  Herculaneum  1800 
years  ago,  still  retain  their  perfect  shape. 


188  METALLOIDS. 

460.  DECOLORIZING    EFFECTS  OF  CHAR- 

Describe  its 

decolorizing       COAL. — Charcoal    has,    also,    the  effect  of 
power.  removing  coloring  matters,  and 

bitter  and  astringent  flavors  from  liquids. 
Thus,  ale  and  porter  lose  both  color  and  fla- 
vor by  being  filtered  through  sugar.  Sugar 
refiners  take  advantage  of  this  property,  in 
decolorizing  their  brown  syrups.  Animal 
charcoal,  or  bone  black,  is  best  adapted  to  these  uses. 
As  an  illustration  of  the  decolorizing  effect  of  char- 
coal, let  water  colored  with  a  few  drops  of  ink,  be 
filtered  through  bone  black.  The  color  will  be  found  to 
disappear,  in  the  process. 

461.  COMBUSTION  OF   CARBON. — All  of 
of  the  <y**-       tne  forms  of  Carbon  are  combustible.   The 
bustionof         combustion  of  charcoal,  in  air,  is  a  famil- 

carbon  ? 

iar  fact.  Its  combustion  in  oxygen  has 
has  been  already  shown.  The  diamond,  and 
plumbago,  will  also  burn  in  a  vial  of  oxygen 
gas,  if  first  intensely  heated.  The  product  of 
their  combustion,  is  precisely  the  same  as  that 
of  charcoal.  From  the  carbonic  acid,  which 
is  produced  in  the  combustion,  the  carbon 
may  be  obtained  in  the  form  of  lamp  black.  The 
nature  of  the  diamond  is  thus  conclusively  established. 

462.  REDUCTION  OF  ORES  BY  CHARCOAL. 

How  does 

charcoal  re-  The  affinity  of  carbon  for  oxygen,  at  a 
duce metals?  high  temperature,  is  very  intense.  It  de- 
prives most  ores  of  their  oxygen,  and  converts  them 
into  metals.  An  agent  which  thus  produces  metals 
from  their  compounds,  is  called  a  reducing  agent,  and 


CARBONIC    ACID.  189 

the  process  is  called  reduction.  Gaseous  carbonic  ox- 
ide, has  the  same  effect  as  carbon,  because  the  affinity 
of  its  carbon  for  oxygen,  is  only  partially  satisfied.  In 
the  process  of  reduction,  these  reducing  agents  are  them- 
selves converted  into  carbonic  acid,  by  the  oxygen  with 
which  they  combine.  Hydrogen  gas,  in  consequence  of 
its  strong  affinity  for  oxygen,  is  also  a  powerful  reducing 
agent.  The  reducing  power  of  carbon  may  be  illus- 
trated by  sprinkling  a  little  litharge  on  ignited  charcoal, 
and  blowing  upon  it  at  the  same  time,  to  maintain  its 
heat.  The  litharge,  or  oxide  of  lead,  will  thus  be  par- 
tially converted  into  globules  of  metal. 


CARBONIC  ACID. 
463.  DESCRIPTION.  —  Carbonic  acid  is  a 

What  ts  car- 

bonic acid?       colorless  gas,  without  much  taste  or  smell, 


eS  l  an(^  ab°ut  one  and  a  nalf  times  as  heavy  as 
air.  Other  properties  are  illustrated  in  the 
experiments  which  follow.  This  gas  is  found  in  many 
mineral  waters,  and  frequently  escapes  from  fissures  in 
the  earth.  It  is  a  constituent  of  all  limestones  and 
and  shells,  forms  ^^Vo-  part  of  the  atmosphere.  It  is 
exhaled  from  the  lungs  of  all  animals,  and  is  a  product 
of  the  combustion  of  coal  and  wood. 

464.  PREPARATION.  —  Carbonic  acid  may 

How  is  carbo- 

nic addpre-      be  prepared  by  burning  charcoal  in  oxygen 
pa1  gas,  as  directed  in   paragraph  461.     Or  it 

may  be  made  by  hanging  a  lighted  candle,  as  long  as  it 
will  burn,  in  a  bottle  filled  with  ordinary  air.     In  this 


190  METALLOIDS. 

case,  the  carbon  of  the  candle  is  converted  into  car- 
bonic acid,  by  the  oxygen  of  the  air.  But  neither 
of  these  methods  give  the  unmixed  gas,  and  that  which 
follows  is  therefore  to  be  preferred. 

465.    ANOTHER    METHOD. — Pour  a  tea- 

Give  the  sec-  •  .       . 

ond  method  of   spoonful    of   muriatic   acid  into   a   large- 
prfpanng  it,      mouthed  half-pint  vial,  and  then 
ad  i  bits  of  marble,   chalk,   or  carbonate   of 
soda,  until  effervescence    ceases.      The  vial 
will  then  be  filled  with  carbonic  acid. 

Explain  the  466.       EXPLANATION. Chalk 

above  process.  an(j  marble  are  both  carbonate  of  lime. 
As  soon  as  they  are  dropped  into  muriatic  acid,  this 
stronger  acid  combines  with  the  lime,  and  retains  it, 
setting  the  carbonic  acid  at  liberty  in  the  form  of  a  gas. 
The  gas  as  it  accumulates,  expels  the  air  from  the  vial, 
and  completely  fills  it.  It  is  obvious  that  in  this  method 
we  do  not  make  carbonic  acid,  but  use  that  which  na- 
ture has  already  made  for  us,  and  imprisoned  in  the 
marble. 

467.  For  most  of  the  experiments  that 

Describe  ano- 
ther method  of   follow,  the  second  simple    method  of  col- 
preparation.      \eci{on  js  sufficient,  and  the  gas  need  not 
be  transferred  to  another  vessel.     When 
it  is  desired  to  obtain  it  separate  from  the 
materials  from  which  it  is  produced,  the 
apparatus  represented  in  the  figure  may 
be  employed. 

468.  CARBONATED  WATERS. 

How  are  car- 

bonatcd waters  Water  absorbs  its  own  volume  of  carbonic 
made  l  acid,  and  thereby  acquires  an  acid  taste. 


CARBONIC    ACID.  191 

The  so  called  "  soda  water,"  or  "  mineral  water,"  is 
prepared  by  confining  water  in  a  strong  metallic  ves- 
sel, and  forcing  into  it  gaseous  carbonic  acid,  by  means 
of  a  forcing-pump.  The  increased  quantity  which  it 
is  thus  made  to  absorb  is  in  precise  proportion  to  the 
pressure  employed.  Neither  of  the  above  names  give 
a  correct  notion  of  the  nature  of  the  ef- 
fervescent drink  referred  to.  It  is  sim- 
ply carbonated  water,  to  which  soda  is 
sometimes  added. 

469.  The  absorption  of  carbonic  acid 
by  water  may  be  shown,  like  that  of 
chlorine,  by  the  method  illustrated  in 
the  figure.  It  may  also  be  shown  by  pouring  a  gill 
of  water  into  a  half-pint  vial  of  carbonic  acid,  and 
then  shaking  it.  The  palm  of  the  hand  being  pressed 
closely  upon  the  mouth  of  the  vial,  the  flesh  will  be 
more  or  less  drawn  in,  to  take  the  place  of  the  gas  ab- 
sorbed. The  vial  maybe  supported  by  this  attach- 
ment. 

470.     EFFERVESCENT  DRINKS. — Cham- 

What  is  said 

of  effervescing  pagne,  sparkling  beer,  and  mead,  congress 
water,  and  similar  drinks,  owe  their  effer- 
vescent qualities  to  this  gas  held  in  solution.  On  expo- 
sure to  the  air,  the  gas  gradually  escapes,  and  the  liquids 
become  insipid  to  the  taste.  The  air  enters  and  takes 
its  place,  expelling  sixty  or  seventy  times  its  own  vol- 
ume of  gas.  This  effect  may  be  hastened  by  striking, 
with  the  hollowed  palm  of  the  hand,  upon  the  top  of 
a  glass  partly  filled  with  one  of  these  liquids ;  there- 
by compressing  the  air,  and  forcing  it  to  enter  rapidly. 


192 


METALLOIDS. 


The  carbonic  acid  immediately  escapes  with  renewed 
and  rapid  effervescence. 

471.     FLAME    EXTINGUISHED 

What  effect 

lias  carbonic        BY     CARBONIC     ACID.  -  Lower      a 

acid  onflame?  lighted  taperj  candle,  or  splinter 
of  wood  into  a  vial  of  carbonic  acid,  pre- 
pared as  before  directed.  The  flame  will 
be  immediately  extinguished,  as  if  it  had 
been  dipped  in  water. 

Give  another  ^^'    ®*    ^    Sam<3    6XPermient    mav 

method  of  per-    performed   by  pouring  the 

££M   §as  into  a  vial-  at  the  bot- 

torn  of  which  is   a  bit  of 

lighted   candle.     Nothing  will  be  seen 

to  flow  from  one  vessel  into  the  other, 

but  the  effect  will  be  the  same  as  before. 

473.    CARBONIC   ACID  is 

Of  what  use 

to  plants  is  FOOD  FOR  PLANTS.  —  Carbonic 

carbonic  acid?     ^^  ig  Qne  Q£  the    principal 

elements  of  the  food  of  plants.  The  leaves  absorb 
it  from  the  air,  and  the  roots  from  the  earth,  and 
convert  it  into  wood  and  fruit.  The  subject  is  fur- 
ther considered  in  the  latter  part  of  this  work. 

474.  IT  is  POISON  FOR  ANIMALS.  —  Wa- 
ter  impregnated  with  carbonic  acid  is  a 
healthful  drink  ;  but  the  same  gas,  when 
taken  into  the  lungs,  produces  death.  It 
operates  negatively,  by  excluding  the  air,  and  also 
positively,  as  a  poison.  Being  heavier  than  the  air, 
lakes  of  this  gas  sometimes  collect  in  the  bottom  of 
caverns.  There  is  a  grotto  of  this  kind  in  Italy,  called 


What  is  the 

effect  of  car- 
b 


CARBONIC  ACID.  193 

the  Grotto  del  Cane,  or  dog's  grotto.  A  man  walking 
into  it,  is  safe,  but  his  dog,  whose  head  is  below  the 
surface  of  the  gaseous  lake,  is  immediately  suffocated. 
Baths  of  carbonic  acid  have  recently  been  employed, 
with  advantage,  in  the  treatment  of  rheumatism,  and 
other  similar  affections,  and  in  cases  of  enfeebled 
vision. 

475.  How  REMOVED  FROM  WELLS.  —  Car- 
bonicacid  re-     bonic  acid  often  collects  in  the  bottom  of 


we^s;  an(l  occasions  danger,  and  some- 
times death,  to  workmen  employed  in 
cleaning  them.  A  candle  previously  lowered  into  the 
well  will,  indicate  the  danger,  if  it  exist.  The  flame 
will  burn  less  brilliantly,  or  be  entirely  extinguished, 
if  much  of  the  gas  is  present.  By  repeatedly  lower- 
ing pans  of  recently  heated  charcoal  into  the  well,  and 
drawing  them  up  again,  the  gas  will  be  absorbed  and 
removed.  The  charcoal  is  first  heated,  to  increase  its 
absorbing  power.  In  this  condition  it  absorbs  thirty- 
five  times  its  own  bulk  of  gas. 

476.  CHARCOAL  FIRES  IN  CLOSE  ROOMS. 

now  does 

burning  char-  Fatal  accidents  not  unfrequently  occur 
To?  accidents?  from  innalmg  the  fumes  of  charcoal,  burned 
in  close  unventilated  rooms.  These  fumes 
consist  of  mingled  carbonic  acid  and  carbonic  oxide. 
The  latter  gas  will  be  hereafter  described. 

477.  SOLIDIFICATION  OF  CARBONIC  ACID. 

How  may  car-     r^          f    •>  .  . 

bonic  acid  be  One  oi  the  most  interesting  of  all  chemical 
solidified?  experiments,  is  the  solidification  of  car- 
bonic acid.  By  combined  cold  and  pres'sure,  this  trans- 
parent gas,  which,  under  ordinary  circumstances,  is  so 

9 


194  METALLOIDS. 

thin  that  the  hand,  passed  through  it,  does  not  recog- 
nize its  presence,  can  be  converted  into  a  solid  snow. 
This  is  done  by  bringing  into  a  strong  iron  cylinder, 
connected  by  a  tube  with  a  second  similar  receptacle, 
the  material  for  making  more  of  the  gas  than  there  is 
room  for  in  the  two  vessels.  The  cylinders  being 
closed,  and  the  gas  produced  by  the  agitation  of  the 
materials,  it  is  evident -that  they  must  burst,  or  the 
gas  must  pack  itself  away  in  some  more  condensed 
form.  The  second  vessel  is  surrounded  by  ice,  and 
kept  extremely  cold,  during  the  process.  In  this  colder 
vessel,  the  gas  assumes  a  liquid  form.  Being  removed 
in  this  condition,  one  portion  of  the  liquid  evaporates 
so  rapidly  as  to  freeze  the  rest.  An  explosive  expan- 
sion of  the  liquid  into  gas  would  naturally  be  antici- 
pated, but  this  does  not  occur.  The  materials  used 
in  the  process  are  sulphuric  acid  and  carbonate  of  soda. 
478.  CARBONIC  OXIDE. — When  carbonic 

How  is  car-  •  -i     •  • 

bonic  oxide  acid  is  passed  through  hot  coals,  it  loses 
half  of  its  oxygen,  and  becomes  carbonic 
oxide.  This  takes  place  in  coal  fires.  The  coal  in 
the  lower  part  of  the  grate,  where  air  is  plenty, 
receives  its  full  supply  of  oxygen,  and  becomes  car- 
bonic acid.  The  hot  coals  above,  where  the  supply 
of  air  is  limited,  take  half  of  the  oxygen  from  the 
carbonic  acid,  and  reduce  it  to  this  oxide,  convert- 
ing themselves  partially  into  carbonic  oxide  at  the 
same  time.  The  new  gas  passes  on  to  the  top  of  the 
fire,  and  there,  where  air  is  again  abundant,  it  burns 
with  a  blue  flame,  and  reconverts  itself  into  carbonic 
acid.  This  gas  is  much  more  poisonous  than  carbonic 


CARBONIC     OXIDE.  195 

acid,  and  is  one  source  of  the  danger  which  arises  from 
open  fires  in  close  rooms.     One-two-hundredth  of  it 
makes  the  air,  if  inhaled  for  any  considerable  time,  a 
fatal  poison. 

479.  COMBUSTION  OF  CARBONIC   OXIDE. 

How  is  car- 

ionic  oxide       For  small  experiments,  the  gas  is  best  pre- 

best  prepared?     ^^    by  coyermg    ft  half  tea-spOOnful    of 

oxalic  acid*  with  oil  of  vitriol,  and  heating  them  to- 
gether in  a  test-tube.  The  gas,  on 
being  kindled  at  the  mouth  of  the 
tube,  burns  with  a  beautiful  blue 
flame.  The  experiment  is  re-ndered 
more  striking,  by  producing  a  jet,  as 
represented  in  the  figure.  The  gas 
thus  obtained  is  really  a  mixture  of 
carbonic  oxide  with  carbonic  acid, 
but  the  admixture  does  not  mate- 
rially affect  the  experiment. 

480.  EXPLANATION. — Each  molecule  of 

Explain  the  . 

formation  of  oxalic  acid  contains  carbon,  oxygen,  and 
carbonic  oxide.  hydrogerij  in  the  proportion  to  form  one 

molecule  each,  of  water,  carbonic  oxide,  and  carbonic 
acid.  Through  the  agency  of  sulphuric  acid,  this  de- 
composition is  accomplished.  The  water  remains  with 
the  acid  while  the  gases  are  evolved. 

481.  IT  PRODUCES    METALS   FROM  OXIDES. 

effect  on  me-  With  the  help  of  a  high  temperature,  car- 
talhc oxides?  bonjc  ox[^e  takes  oxygen  from  oxides, 

and  converts  them   into  metals.     It  contains  oxygen 

*  This  acid  has  the  appearance  of  a  salt,  and  is  poisonous. 


196  METALLOIDS. 

already,  but  its  chemical  appetite  is  only  half  satisfied 
with  that  element.  It  is  this  gas,  produced  in  the  fire, 
as  before  described,  which  converts  iron  ores  into  metal, 
in  the  smelting  furnace.  It  is  itself  converted  into  car- 
bonic acid  at  the  same  time. 

SILICON. 

What  is  sili-  482.  DESCRIPTION. — Silicon  is  a  dark 
con  ?  gray  substance,  possessed  of  metallic  lustre, 

but  classed  with  the  metalloids,  because  it  resembles 
them  in  its  compounds.  It  is  also  called  silicium. 
It  is  prepared  from  silica,  by  the  method  hereafter  de- 
scribed for  the  production  of  calcium  from  lime. 

483.  SILICIC  ACID  OR   SILICA. — Quartz 
*icaf  ^  Sll~      or  roc^  crvstalj  is  nearly  pure  silica.     Sea- 
sand,   opal,  jasper,   agate,    cornelian,    and 

chalcedony,  are  other  forms  of  the  same  substance. 
It  forms  also  part  of  a  very  abundant  class  of  rocks,  called 
silicates,  and  probably  forms  one-sixth  of  the  mass  of 
the  earth. 

484.  SOLUBLE  SILICA. — Silica   may   be 

How  can  silica 

be  made  solu-  •  dissolved  in  water,  by  first  fusing  it  with 
a  large  proportion  of  potash.  On  then  ad- 
ding acid,  to  neutralize  the  potash,  the  silica  precipitates 
in  the  form  a  jelly.  By  this  circuitous  process,  the 
most  gritty  sand  is  converted  into  a  soft  jelly.  A  sin- 
gular application  of  this  rock-jelly,  in  the  adulteration 
of  butter,  has  recently  been  detected  in  England.  Dis- 
solved silica  also  occurs  in  nature,  and  hardens  into 
agates,  onyx,  and  other  precious  stones. 


BORON.  197 

485.  PETRIFACTIONS.  —  As  wood  wastes 
What  is  the 

cause  of  pet-     away  in  certain  sihcious  waters,  the  par- 

rifaction? 


of  the  departing  atoms,  and  thus  copy  the  wood  in 
stone.     Such  copies  are  called  petrifactions. 


BORON. 

What  is  60-  486.  DESCRIPTION.  —  Boron  is  a  brown 

ron  ?  powder,  never  seen  except  in  the  chemists 

laboratory,  and  of  no  practical  value.  It  occurs  in 
nature,  combined  with  other  elements,  as  borax  arid 
boracic  acid. 

487.  BORACIC  ACID.  —  This  acid  is  com- 

Hoio  'is  bora- 

cic acid  form-  monly  seen  in  the  form  of  white  pearly 
scales.  It  exhales  with  volcanic  vapors 
which  issue  from  the  earth  in  Tuscany.  These  va- 
pors are  condensed  in  water,  and  the  solid  acid  is 
obtained  by  evaporating  the  solution.  The  acid  is  used 
like  borax,  as  a  flux.  It  is  bitter,  rather  than  sour,  to 
the  taste,  but  is  called  an  acid  because  it  forms  salts. 


HYDROGEN. 
488.  DESCRIPTION  AND   OCCURRENCE. — 

What  is  hy-  •  i      i  AS 

drogen?  Hydrogen  is  a  colorless  gas,  about  one  fif- 

occurl  dOCS  U     teenth  aS   heaVy  aS    the  air'       li    1S  °f  SUch 

extreme  tenuity,  that  it  may  be  blown 
through  gold  leaf,  and  kindled  on  the  opposite  side. 
One-ninth  part  of  the  ocean,  and  the  same  proportion 
of  all  water  in  existence,  is  hydrogen  gas.  It  enters, 


198  HYDROGEN. 

also,   largely  into  the   composition  of  all  animal  and 

vegetable  matter,  and  forms  the  basis  of  most  liquids. 

489.    PREPARATION.  —  Introduce  a   few 

Describe  the 

method  of  pre-    bits  of    iron  or  zinc 

paring  iff  ^   ft    yial    one_third 


filled    with    water.     Add   a   tea- 

spoon-full   or   more    of  common 

sulphuric  acid,  and  attach  to  the 

vial  a  bent  tube  or  a  clay  pipe, 

as  represented  in  the  figure.     The  evolution  of  the  gas 

immediately  commences.     The   first  portions,  which 

contain  an  admixture  of  air,  are  allowed  to  escape  ;  the 

pipe-stem  is  then  brought  under  the  mouth  of  the  vial, 

and  the  gas  collected.* 

590.   EXPLANATION.  —  Water  is  compos- 

Explain  the 

formation  of     ed  of  oxygen  and  hydrogen  gases.     Each 

hydrogen?          WQuld   be  &     ag    but    for 


holds  it  in  the  liquid  form.  In  the  above  process  for 
preparing  hydrogen,  the  zinc  is,  as  it  were,  the  ransom 
paid  for  its  liberation.  The  oxygen  combines  with 
the  zinc  and  the  hydrogen  escapes. 

491.  Pure  water  will  not  suffice  in  the 

What  purpose 

is  served  by       process.     It  must  contain   acid,   to  unite 

the  acid?  with    the  Qxide    of   zinc?  as  fagt  ag  formecl> 

The  presence  of  an  acid,  for  which  the  oxide  has  great 
affinity,  seems  to  stimulate  its  formation.  It  may, 

*  When  a  taper  can  be  applied  at  the  mouth  of  the  pipe-stem  without 
explosion,  it  may  be  certainly  known  that  an  unmixed  gas  is  in  pro- 
cess of  evolution.  A  cloth  should  be  thrown  over  the  vial  and  this  test 
made  before  commencing  the  collection.  The  connection  of  the  ap- 
paratus in  the  above  experiment  is  made  with  a  paper  stopper,  formed 
on  a  bit  of  pipe-stem  or  glass  tube. 


HYDROGEN.  199 

indeed,  be  regarded  as  a  general  law,  that  the  pres- 
ence of  acids  promotes  the  formation  of  oxides,  and 
vice  versa. 

492.     ANOTHER     METHOD. — Hydrogen 

Give  another  J 

method  ofpre-  may  also  be  made,  by  passing  steam  through 
a  heated  gun-barrel,  containing  bits  of 
iron.  Bundles  of  knitting  needles  are  commonly  em- 
ployed for  the  purpose.  The  steam  leaves  its  oxygen, 
combined  with  the  iron,  and  escapes  as  hydrogen  gas. 

493.  COMBUSTION  OF  HYDROGEN. — Bring 

What  i*  pro-  ,  , 

duced  by  the  a  dry,  cold  tumbler,  over  a  burning  jet  of 
combustion  of  hydrogen.  The  vessel  will  soon  become 

hydrogen  f 

moistened  on  the  interior.  The  water 
thus  produced,  is  a  result  of  the  combination  of  hydro- 
gen with  oxygen  of  the  air.  But  for  the  cold  surface, 
with  which  it  is  brought  into  contact,  it  would  have 
escaped  into  the  air  as  vapor.  The  composition  of 
water  was  shown  in  Part  1.,  (•§>  277,)  by  galvanic  de- 
composition. It  is  here  demonstrated  by  combining 
its  elements,  and  thus  reproducing  it.  Water  is  also 
formed  in  the  combustion  of  any  substance  containing 
hydrogen  as  one  of  its  constituents.  The  above  expe- 
riment may  therefore  be  made  with  a  lighted  lamp  or 
candle,  as  well  as  with  the  jet  of  pure  hydrogen. 

494.  EXPLOSION  OF  MIXED  OXYGEN  AND 

How  is  an  ex- 
plosive mix-      HYDROGEN. — Allow  oxygen  to  flow  into  an 
turcprepared?    inverte(i  ^  as  directed  in  para- 
graph 330,  until  it  is  one-third  full.    Fill  it  up 
with  hydrogen,  collected  as  shown  in  Par.  489. 
Cork  the  vial  under  water.     It  is  now  filled  with 
an  explosive  mixture,  which  may  be  fired  by  the 


200  METALLOIDS. 

application  of  a  taper.  To  secure  against  accident,  the 
precaution  should  invariably  be  observed,  of  winding 
the  vial  with  a  towel,  before  the  discharge. 

495.   EXPLANATION.  —  The  explosion  re- 

Why  does  this 

mixture  ex-        suits  from  the  fact  that  all  of  the  hydrogen 


plode?  ^n  tjie  v-aj  kurns  at   oncej  causing   great 

heat,  and  sudden  expansion  of  vapor.  The  combus- 
tion is  thus  simultaneous,  because  oxygen,  the  sup- 
porter of  combustion,  is  present  at  every  point.  When, 
on  the  other  hand,  a  jet  of  hydrogen  is  kindled,  no 
explosion  occurs,  because  the  combination  is  gradual. 
Combustible  hydrogen  meets  with  oxygen  in  this  case, 
only  on  the  surface  of  the  jet. 

n   ,  -i  th  496.   THE  HYDROGEN  GUN.  —  The  expe- 

hydrogen  gun,    riment  for  the  explosion  of  mixed  hydro- 

and  the  me-  -,      .  -,  -, 

thodofcharg-  gen  and  oxygen  gases,  may  be  made  in  a 
ing  it.  strong  tin  tube,  provided  with  a  vent  near 

the  closed  end.  Such  a  tube,  about  an  inch  in  diame 
ter,  and  eight  inches  in  length,  is  called  the  hydrogen 
gun.  In  loading  it,  the  vent  is  stopped  with  wax, 
the  tube  filled  with  water,  and  the  gases,  previ- 
ously mixed  in  the  right  proportion,  poured  upward 
into  it,  as  indicated  in  the  figure.  The 
gun,  being  thus  loaded,  is  tightly 
corked,  under  water,  and  afterward 
fired  at  the  vent.  The  explosion  is 
sufficient  to  expel  the  cork  with  vio- 
lence, accompanied  by  a  loud  report. 
The  vial  from  which  the  tube  is  loaded 
must  not  be  too  large,  or  it  will  not  be  practicable  to 
turn  it  and  pour  upward,  as  desired.  This  difficulty 


HYDROGEN.  201 

may  also  be  obviated,  by  the  substitution  of  a  water- 
pail,  for  the  bowl  represented  in  the  figure. 

497.  CHARGE  OF  AIR    AND    HYDROGEN. 

Describe  an- 
other explosive    As    air    contains    uncombmed    oxygen,   a 

mixture  of  air  and  hydrogen  also  forms  an 
explosive  mixture.  But,  as  air  is  only  one-fifth  oxy- 
gen, five  times  as  much  of  it  must  be  used ;  in  other 
words,  five  parts  of  air  are  required,  for  every  two 
parts  of  hydrogen.  To  make  the  mixture,  hydrogen 
may  be  led,  as  before,  into  an  inverted  vial,  a  little 
more  than  two-thirds  full  of  air.  The  exact  propor- 
tion is  not  essential  in  this,  or  any  similar  case  of  ex- 
plosive mixture. 

498.  A  SIMPLER  METHOD. — A  simpler 

Give  a  sim-  ,-•/., 

pier  method  method  of  loading  the  gun,  or  charging 
°^adin9the  the  vial  with  the  explosive  mixture,  is  to 
invert  it  over  a  jet  of  hydrogen,  as  repre- 
sented in  the  figure.  The  pipe-stem,  or  tube, 
which  conveys  the  gas,  is  previously  wound 
with  paper,  till  it  occupies  about  two-thirds  of  the 
inner  space  of  the  gun.  Escaping  hydrogen  fills 
the  remainder.  On  withdrawing  the  tube,  air 
enters  to  take  its  place,  and  the  gun  is  thus 
charged  with  mixed  air  and  hydrogen,  in  the  right 
proportions.  It  is  then  corked  and  fired.  This 
experiment  may  also  be  made  with  a  test-tube, 
discharging  it  at  the  mouth.  Explosions  with  mixed 
air  and  hydrogen,  are,  of  course,  less  violent  than 
where  pure  oxygen  is  used  instead  of  the  diluted  oxy- 
gen of  the  air. 

Docs  hydrogen  499.    HYDROGEN  WILL  NOT  SUPPORT   COM- 

support    com-  '  %  .    J  .:  ; 

bustion?  BTTSTION. — Flame   is  extinguished  in  hy- 

9* 


202  METALLOIDS. 

drogen,  as  it  would  be  in  water.  Re-charge  the  gas 
bottle,  if  necessary,  and  hang  a  second  large-mouthed 
vial  above  it,  as  represented  in  the  figure.  Af- 
ter a  few  minutes,  it  may  be  presumed  that 
the  tipper  vial  is  filled  with  hydrogen.  Apply 
a  lighted  match  to  its  mouth,  and  the  gas  will 
inflame,  and  continue  to  burn  with  a  faint 
light.  Introduce  a  second  taper,  as  represent- 
ed in  the  figure.  It  will  be  kindled  at  the 
mouth  of  the  bottle,  and  again  extinguished 
above.  The  match  is  extinguished,  because,  a  little 
abo've  the  mouth  of  the  vial,  there  is  no  oxygen  to  sup- 
port the  combustion  of  the  carbon  and  hydrogen,  of 
which  it  is  composed. 

500.     HYDROGEN    MADE    BY  THE  METAL 

Describe  the  ./*,-, 

preparation       SODIUM.  —  Another  very  beautiful,  but  more 
expensive    method  of   making    hydrogen 


gas,  is  as  follows.     Fasten  a  piece  of  me- 
tallic sodium,  of  the  size  of  a  pep- 
per-corn, upon  the  end  of  a  wire,  and 
thrust  it  suddenly  under  the  end  of 
a  test-tube  filled  with  water,  and  held 
very  near  the  surface,  as  represented 
in  the  figure.     The  metal  melts  as  soon  as  it  touches 
•  the  water,  and  rises  to  the  top  of  the  tube.     Hydrogen 
is  immediately  formed,  and  displaces  the  water,  fill- 
ing the  tube  rapidly  with  the  liberated  gas. 
Explain  the          501.   EXPLANATION.  —  Sufficient  heat  is 
process.  evolved  by  the  action  of  sodium  on  water 

to  fuse  it  at   once.     The  metal  is  lighter  than  water, 
and  therefore  rises  to  the   top  of  the   tuba.     At  this 


WATER.  203 

point  the  chemical  process  begins.  Sodium  has  the 
most  intense  affinity  for  oxygen,  and  therefore  com- 
bines with  this  element  of  the  water,  setting  its  hydro- 
gen at  liberty.  No  acid  is  required  as  in  the  case  of 
zinc.  Metallic  potassium  may  also  be  used  in  this 
experiment.  To  avoid  its  ignition  by  contact  with 
the  water,  it  is  to  be  wrapped  in  paper,  and  the  twisted 
end  of  the  wrapper  used  as  a  holder,  with  which  to 
thrust  it  under  the  mouth  of  the  tube. 


WATER. 
502.    COMPOSITION. — Many    important 

Of  what  is  ,     J  _ 

water  com-  properties  of  water  have  already  been  il- 
posed  lustrated  in  the  chapter  on  Vaporization. 

Others  will  be  mentioned  below.  It  is  composed  of 
oxygen  and  hydrogen,  as  has  already  been  proved  both 
by  analysis  and  synthesis.  These  gases  are  condensed 
in  combination  to  about  a^Vo-  of  their  original  volume. 
It  remains  to  show  how  the  exact  proportion  in 
which  they  enter  into  the  composition  of  water  is  as- 
certained. 

503.     FIRST    METHOD  OF  PROOF. — One 

Describe  the  . 

method  by  gal-  method  is  to  decompose  water  by  the  gal- 
vanic  Process>  and  collect  and  weigh  the 
gases  obtained.  The  oxygen  is  found  to 
weigh  eight  times  as  much  as  the  hydrogen.  Water 
is  thus  shown  to  be  composed  of  eight  parts  of  oxygen, 
by  weight,  to  one  part  of  hydrogen.  In  other  words, 
nine  pounds  of  water  contain  eight  pounds  of  oxygen 
and  one  pound  of  hydrogen. 


204  METALLOIDS. 

504.  SECOND  METHOD. — Another  method 

Show  how  com-     .  -,•->-> 

.position  by       is  to  measure  the  gases    obtained  by  the 

7al9culatedy  ^  same  method  of  decomposition.  Two 
from  measure,  measures  of  hydrogen  are  thus  obtained  for 
every  single  measure  of  oxygen.  The  chemist  then  pro- 
ceeds to  calculate  the  relative  weight.  Knowing  before- 
hand that  hydrogen  is  the  lighter  gas,  weighing  but 
one-sixteenth  as  much  as  the  same  quantity  of  oxygen, 
he  infers  that  the  double  volume  obtained  in  the  above 
experiment,  weighs  but  one-eighth  as  much  as  the 
oxygen  obtained  in  the  same  decomposition.  The 
result  of  this  indirect  process  is  the  same  as  that  stated 
at  the  conclusion  of  the  last  paragraph. 
Describe  the  °Q5-  THIRD  METHOD. — A  third  method 

third  method,  consists  in  the  reproduction  of  water  from 
mixed  hydrogen  and  oxygen,  observing  at  the  same 
time  the  quantities  in  which  they  combine.  This  may 
be  readily  effected  in  a  test-tube.  The  gases  being 
introduced  into  the  tube  in  about  the  right  proportion, 
and  in  small  quantity,  its  extremity  is 
then  intensely  heated.  A  slight  explo- 
sion and  combination  of  the  gases  is  the 
result,  and  the  water  rises  to  take  their 
place,  mingling  with  the  small  quantity 
of  water  produced  in  the  experiment.  Any  excess  of 
either  gas  remains  uncombined.  Whether  this  surplus 
is  oxygen  or  hydrogen,  may  be  readily  proved  by 
methods  previously  given.  This  excess  being  sub- 
tracted from  the  quantity  of  the  same  gas  originally 
used,  shows  the  proportion  in  which  the  combina- 
tion has  occurred. 


WATER.  205 

506.  The  explosion  may  be    avoided, 

How  may  the  .  ' 

explosion  be  and  a  gradual  combination  of  the  gases  ef- 
fected, by  evaporating  a  few  drops  of  pla- 
tinum solution  in  the  test-tube,  and  igniting  the  residue 
previous  to  the  commencement  of  the  above  experi- 
ment. A  ball  of  fine  iron  wire  is  then  crowded  into 
the  end  of  the  tube.  The  mixture  of  gases  being 
finally  introduced,  the  least  touch  of  flame  upon  the 
end  of  the  tube  is  sufficient  to  effect  a  gradual  combi- 
nation. For  an  explanation  of  the  agency  of  plati- 
num in  the  above  experiment,  the  student  is  referred 
to  the  chapter  on  metals.  The  iron  wire  serves  to 
prevent  ignition,  and  consequent  explosion,  by  appro- 
priating part  of  the  heat  produced  by  the  combination 
of  the  gases.  The  form  of  the  experiment  last  de- 
scribed, is  the  only  one  that  can  be  recommended  to 
the  student.  With  the  security  against  explosion 
which  it  affords,  a  test-tube  filled  with  the  mixed  gases 
may  be  submitted  to  experiment.  Where  very  accu- 
rate results  are  sought,  the  process  must  be  conducted 
in  a  carefully  graduated  tube.  By  employing  mercury 
instead  of  water,  the  water  produced  in  the  experiment 
may  be  seen. 

507.    FOURTH   METHOD. — Still  another 

Give  the  meth-  .  . 

od  by  oxide  of    method  is  illustrated  in  the  figure.     It  con- 
essential- 


ly,  in  the  production  of 
water  from  its  elements  as 
before  ;  furnishing,  at  the 
same  time,  the  means  of  as- 
certaining the  proportional  weight  of  the  gases,  which 
have  taken  part  in  its  formation.  The  tube  most 


206  METALLOIDS. 

distant  from  the  aspirator*  is  first  filled  with  oxide  of 
copper,  and  then  heated  while  a  current  of  hydrogen 
gas  is  drawn  over  its  surface.  The  heated  hydrogen 
carries  with  it  the  oxygen  of  the  copper,  and  passes 
into  the  second  tube,  as  vapor  of  water.  Here  it  is  re- 
tained by  potassa,  or  some  substance  of  similar  proper- 
ties. Both  tubes  are  afterward  weighed,  and  their  gain 
or  loss  determined,  by  comparison  with  their  weight 
before  the  commencement  of  the  process. 

508.  The  loss  of  weight  in  the  one  tube. 

How  are  the 

results  calcu-  expresses  the  weight  of  the  oxygen  which 
it  has  furnished  for  the  formation  of  water  ; 
the  gain  in  the  second  tube,  gives  the  weight  of  the  water 
thus  formed.  The  difference  of  the  two,  gives  the 
weight  of  the  hydrogen  which  has  been  appropriated 
in  its  passage,  and  now  makes  part  of  the  newly  formed 
water.  For  every  nine  grains  of  water  thus  produced, 
it  is  found  that  eight  grains  of  oxygen,  and  one  of  hy- 
drogen have  been  consumed.  Its  precise  composition 
is  thus  demonstated,  by  another  and  quite  distinct  pro- 
cess. 

What  is  said  5®$>  SOLUTION. — Water  is  a  very  gene- 
of  solution  ?  rai  soivent.  The  disappearance  of  salt,  or 
sugar,  in  water,  is  an  example.f  Transparency  is  es- 
sential to  a  solution.  Where  the  particles  of  a  solid 
are  distributed  throughout  a  liquid,  as  when  chalk  is 

*  A  vessel  employed,  as  in  the  present  instance,  to  produce  a  current 
of  air  or  gas,  is  called  an  aspirator. 

t  Water  also  di-solves  many  gases.  The  ammonia  of  the  shops  is 
prepared  by  passing  gaseous  ammonia  in  water. 


WATER.  207 

stirred  with  water,  it  is  said  to  be  diffused,  instead  of 
dissolved.  The  solvent  action  of  water  plays  a  most 
important  part  in  nature,  as  will  be  seen  in  the  conclu- 
ding chapter  of  this  work.  The  subjects  of  solution, 
and  precipitation,  are  more  fully  considered  in  the 
chapter  on  Salts. 

Wkatispre-  ^10.  PRECIPITATION. — Where  a  substance 
dpitation  ?  which  has  been  dissolved,  is  re-converted 
into  a  solid  form,  it  is  said  to  be  precipitated. 
Thus,  when  air  from  the  lungs  is  blown 
through  a  quill  or  pipe-stem  into  water,  the 
lime  combines  with  the  carbonic  acid  from  the 
lungs,  and  falls  to  the  bottom  of  the  vessel,  in 
the  form  of  solid  particles  of  chalk.  The 
solid  thus  produced,  is  called  a  precipitate. 

511.  FILTRATION. — Filtration  is 

What  is  filtra- 
tion, and  hoio    the    separation    of    a    precipitate 

is  it  effected?      from  the  Uquid  m  which  it  jg  con- 

tained.  This  is  effected  by  throwing  the  mix- 
ture into  a  paper  cone,  which  retains  the 
solid,  while  the  liquid  passes  through  its  pores. 
Such  a  filter  is  prepared  by  folding  unsized  paper  into 
the  shape  of  a  quadrant,  which  is  then  opened,  so  as 
to  form  a  cone,  commonly  supported  in  a  glass  funnel. 
It  is  possible,  in  small  experiments  to  dispense  with  the 
funnel,  as  is  done  in  the  figure,  and  even  to  use  ordi- 
nary newspaper,  in  the  place  of  that  especially  pre- 
pared for  the  purpose. 


208  METALLOIDS. 

5 12.     CRYSTALLIZATION. — Dissolve 

Howmaycrys-         ir  i       r     i  •  •  ^ 

ta^s  of  alum  be  hall  a  pound  oi  alum  in  a  pint  of 
obtained?  boiling  water,  and  hang  a  cotton  cord 
in  the  vial.  As  the  water  cools,  crystals  will  form 
on  the  thread.  Bonnet  wire  may  be  bent  into  the 
shape  of  baskets,  miniature  ships,  &c.,  and  cov- 
ered, by  this  means,  with  a  beautiful  crystalliza- 
tion. 

Explain  the  513.  EXPLANATION. — Hot  water  has  for 

process.  most    substances     greater    solvent    power 

than  cold  water.  In  the  case  of  alum,  for  example,  water 
slightly  warmed,  will  dissolve  twice  as  much  as  cold 
water.  It  follows,  that  as  the  hot  water  becomes  cold, 
part  of  the  alum  must  become  solid  again.  In  so 
doing,  the  particles,  in  obedience  to  their  mutual  at- 
traction, arrange  themselves  in  crystals,  as  described 
in  the  first  Chapter  III. 

514.  SNOW  CRYSTALS. — Snow  flakes  are 

What  is  said  1-1 

of  snow  crys-  always  either  grouped  or  single  crystals, 
and  their  form  may  often  be  distinctly  seen 
with  the  naked  eye.  They 
are  best  observed  by  catching 
them  upon  a  hat,  or  other 
dark  object,  and  inspecting  them  in  the  open  air. 

515.  CHEMICAL  COMBINATIONS. — Water 

What  is  said 

of  the  combi-     unites   with  both  bases  and  acids,  to  form 

nations  of  wa-     hydrate^       Thus?    ^^    lim^  ^  formg  hy_ 

drate  of  lime  ;  with  sulphuric  acid,  hy- 
drated  sulphuric  acid.  Most  of.  the  oxygen  acids,  in 
the  form  in  which  we  employ  them,  contain  water  in 
a  state  of  combination,  and  are  therefore  hydrated 


WATER.  209 

acids.     They  may  also  be  regarded  as  salts,  of  which 
oxide  of  hydrogen  or  water  is  the  base. 

What  is  said  516.     RELATIONS  TO  LIFE. Water  forms, 

feiatioLfo  US   by  far'  the  Sreater  Part  of  a11  animal  and 
life?  vegetable  matter,   as  will    be    more   fully 

seen  in  the  portion  of  this  work  which  treats  of  or- 
ganic chemistry.  To  water,  the  leaf  of  the  vegetable 
and  the  muscle  of  the  animal,  owe,  in  a  great  degree, 
their  pliancy  and  freedom  of  motion.  In  view  of  these 
and  other  relations  to  life,  the  negative  properties  of 
water  are  not  the  least  important.  Had  it  taste,  01 
odor,  however  exquisite,  we  should  soon  weary  of  them. 
And  but  for  its  mild  and  neutral  character,  it  would 
irritate  the  delicate  nerves  and  fibres  which  it  bathes. 
517.  At  very  high  temperatures  the  va- 

Whnt  is  the  J 

effect  of  water  por  of  water  decomposes  many  minerals, 
ratureksfmp€'  and  exPels  strong  acids  from  their  com- 
pounds. Under  the  stimulating  influence 
of  heat,  this  neutral  liquid  becomes  a  chemical  agent 
of  extreme  energy.  Such  decompositions  as  are  here 
referred  to,  are  without  doubt,  constantly  going  on  be- 
neath the  surface  of  the  earth. 


COMPOUNDS    OF    HYDROGEN,  WITH   CHLORINE,  BROMINE, 
IODINE,  FLUORINE,  AND  SULPHUR. 

Under  this  head  are  to  be  described  a  new  series  of 
acids,  distinguished  by  the  absence  of  oxygen  from  all 
which  have  hitherto  been  mentioned  The  molecules 
of  each,  like  those  of  water,  are  composed  of  single 
atoms  of  their  constituents. 


210  METALLOIDS. 

They  are  all  gaseous,  and  are  sometimes  called  hy- 
dracids,  from  the  hydrogen  which  enters  into  their  com- 
position. Their  salts  are  described  in  Chap.  III. 

HYDROCHLORIC  ACID. 

518.    DESCRIPTION. — Hydrochloric  acid 
*s  a  c°l°rless  gasj  fuming,  by  contact  with 
add?     What    the  air.     It  sometimes  issues  from  volca- 

is  said  of  its  ,         .       ,,        .  . ,,    .    , 

occurrence?       noes,  but  is,  tor  the  most  part,  an  artificial 
product.     Its  solution  in  water  is  known 
as  muriatic  acid. 

519.  PREPARATION. — Gaseous  hydro- 
prepa'ratlon.  chloric  acid,  may  be  produced,  like  water, 
by  the  direct  combination  of  its  elements. 
For  this  purpose,  equal  volumes  of  the  two  gases  are 
mixed  by  candle-light,  or  in  carefully  covered  bottles, 
and  then  exposed  to  the  direct  rays  of  the  sun.  The 
action  of  the  light  is  so  intense,  that  on  throwing  a 
bottle,  thus  filled,  from  shadow  into  sunlight,  it  imme- 
diately explodes.  The  explosion  is  a  consequence  of 
the  energetic  union  of  the  two  gases,  under  the  influ- 
ence of  the  chemical  rays  of  the  sun.  The  acid  pro- 
duced is  at  once  dissipated  in  the  air.  Great  caution 
should  be  used  in  this  experiment,  for  even  the  diffused 
light  of  day  has  been  known,  in  some  instances,  to 
occasion  explosion. 

520.    ANOTHER  METHOD. — Hydrochloric 

Describe  an- 

other  mode  of  acid  may  also  be  made  from  common  salt, 
preparing  it  ?  which  fumishes  the  chlorine,  and  ordinary 
hydrated  sulphuric  acid ,  which  furnishes  the  hydrogen. 


HYDROCHLORIC    ACID. 


211 


A  tea-spoonfull  of  common  salt  is  introduced  into  a 
test-tube,  with  about  the  same 
bulk  of  water.  Half  as  much 
acid  is  added,  then  the  mixture 
gently  heated,  and  the  acid  gas 
led  into  water,  as  shown  in  the 
figure.  Water  absorbs,  at  ordi- 
nary temperatures,  480  times 
its  own  volume,  of  the  gas. 
There  is  no  occasion,  for  the 

purpose  of  experiment,  to  carry  on  the  process  till  it  is 
thus  saturated.     A  few  minutes  will  suffice  to  make  an 
acid  strong  enough  to  dissolve  zinc. 
Explain  the          52 1.  EXPLANATION. — Hydrated  sulphu- 
process.  rjc  %(,[&  fras  always  a  strong  tendency  to 

form  metallic  salts.  In  this  case  it  takes  the  metal, 
sodium,  from  the  common  salt,  and  thereby  converts 
itself  into  sulphate  of  soda.  At  the  same  time  it  gives 
back  hydrogen  to  the  salt,  in  place  of  its  lost  sodium, 
converting  it,  by  the  exchange,  into  hydrochloric  acid. 
The  process  just  described,  is  the  one  always  employed 
in  the  manufacture  of  hydrochloric  acid. 

522.  ACTION  OF  HYDROCHLORIC  ACID  ON 

What  metals  ,,     ,        .  ,  -IT        i 

does  hydro-  METALS. — Hydrochloric  acid  dissolves  tm> 
chloric  dis-  an(j  a]j  of  fae  meta|s  which  precede  it  in 

solve  ? 

the  chapter  upon  metals.     For  tin,  a  hot 
and  concentrated  acid  must  be  employed. 

523.  The   solution  depends  on  the  fact 

On  what  does 

the  solution  that  the  metals  take  chlorine,  from  the 
depend?  hydrochloric  acid,  thereby  converting 

themselves  into  soluble  chlorides.     The  hydrogen  then 


212  METALLOIDS. 

assumes  the  gaseous  form,  and  escapes  with  lively  ef- 
fervescence.    An  experiment  may  best  be  made  with 
zinc,  to  which  a  little  dilute  acid  is  added. 
What  is  aqua        524.  AQUA  REGiA. — On  mixing  muriatic 
regia?  ac{^  with  half  of  its  bulk  of  strong  hydro- 

chloric acid,  aqua  regia  is  produced  ;  so  called,  from  its 
regal  power  over  the  noble  metals.  Gold  and  platinum, 
which  are  not  effected  by  either  acid  alone,  dissolve 
readily  in  aqua  regia.  The  solvent  power  of  aqua  re- 
gia depends,  as  before  explained,  on  the  nascent  chlo- 
rine which  it  supplies. 

525.  HYDROBROMIC  AND  HYDRIODTC  ACIDS. 

^lobromicand  These  acids  are  of  interest  to  the  chemist 
hydriodie  only.  They  resemble  hydrochloric  acid, 

acids  ?  .  . 

in  being  colorless  gases,  strongly  acid, 
soluble  in  water,  and  capable  of  dissolving  many 
metals. 


HYDROFLUORIC  ACID. 

526.  DESCRIPTION. — Hydrofluoric  acid 

What  is  hy- 
drofluoric         is  a  colorless,  corrosive  gas,  acting  on  glass, 

and  many  minerals  which  other  acids  do 
not  affect.  It  condenses  into  a  liquid,  at  the  freezing 
point  of  water.  It  is  not  known  to  occur  ready  formed 
in  nature. 

527.  PREPARATION. — Hydrofluoric  acid 

How  is  hydro- 

fluoric  acid       is  made  Irom  a  mineral  called  fluor  spar, 
prtpar  by  ttie  game  meai)S  employed  to  make  hy- 

dochloric  acid.     On  account  of  its  corrosive  action  on 
glass,  vessels  of  lead  or  platinum  are  employed  in  the 


HYDROFLUORIC    ACID.  213 

process.  This  gas  is  so  poisonous,  when  inhaled,  and 
its  solution  so  corrosive  to  the  skin,  that  its  prepara- 
tion, in  any  considerable  quantity,  should  be  left  to  the 
experienced  chemist. 

Explain  the  ^28.    EXPLANATION. In    the  above    pro- 

process  ?  cess,  the  fluor  spar,  which  is  a  fluoride  of 

calcium,  furnishes  the  fluorine,  and  hydrated  sulphuric 
acid,  the  hydrogen.  The  remaining  constituents  unite 
to  form  sulphate  of  lime,  which  remains  in  solution. 

529.  ETCHING  ON  GLASS. — It  has  already 
cess  for  etch-  been  stated  that  hydrofluoric  acid  attacks 
wg  glass.  glass,  and  many  minerals.  By  covering 
with  wax,  they  may  be  protected  against  the  corrosion. 
Advantage  is  taken  of  these  two  facts  in  etching 
upon  glass.  The  surface  is  first  slight- 
ly warmed  and  rubbed  with  beeswax, 
and  then  warmed  again,  to  produce  an 
even  coating.  Figures,  or  letters,  are 
then  drawn  upon  the  glass,  through  the  wax,  with 
a  pen-knife,  or  other  pointed  instrument.  The  plate, 
being  now  exposed  for  a  few  minutes,  to  the  fumes 
of  hydrofluoric  acid,  and  the  wax  subsequently  re- 
moved, is  found  to  be  deeply  etched.  Fumes  of  hy- 
drofluoric acid,  for  the  purpose,  are  best  obtained  by 
placing  a  half  tea-spoonful  of  pulverized  fluor  spar, 
in  a  warm  tea-cup,  and  covering  the  powder  with  oil 
of  vitriol.  A  little  ether,  or  potash,  will  be  found  of 
use  in  removing  the  last  portions  of  wax  from  the 
plate. 

Explain  the  530.      EXPLANATION. As  OXygeil    COm- 

above  process,     bines  with  carbon  to  form  carbonic  acid,  so 


214  METALLOIDS. 

the  hydrofluoric  acid  eats  out  the  silicon  of  the  glass, 
where  it  is  exposed,  and  passes  off  with  it,  in  the  form 
of  a  new  and  more  complex  gas.  A  solution  of  the 
gas  may  be  prepared  by  the  process  employed  for  hy- 
drochloric acid.  Bottles  of  vulcanized  India  rubber, 
or  gutta  purcha,  may  be  used  in  keeping  the  solution. 

HYDROSULPHURIC  ACID. 
531.  DESCRIPTION — Hydrosulphuric  acid 

What  is  hy-          . 

dromlphuric  is  a  colorless  gas,  also  known  as  sulphu- 
retted hydrogen.  It  has  a  putrid  odor  and 
feeble  acid  properties.  Like  the  rest  of  the  series,  it 
is  soluble  in  water.  It  occurs  in  many  natural  waters, 
called  sulphur  springs.  It  is  one  of  the  products  of 
the  decomposition  of  animal  matter,  and  the  source  of 
much  of  the  disgusting  odor  which  they  emit  during 
putrefaction. 

Howisitpre-  ^32.  PREPARATION. — It  is  made  from 
pared?  sulphuret  of  iron,  as  hydrochloric  acid 

is  made  from  common  salt  ;  and  hydrofluoric  acid 
from  fluor  spar.  In  the  above  process,  sulphuret 
of  iron  furnishes  the  sulphur,  and  hydrated  sul- 
phuric acid,  the  hydrogen.  The  remaining  elements 
unite  to  form  sulphate  of  iron,  which  remains  in  solu- 
tion. On  account  of  the  disgusting  smell  of  the  gas, 
it  is  best  to  prepare  it  only  in  small  quantities. 

533.    DISCOLORATION    OF    METALS    AND 

What  effect 

has  it  on  met-     PAINTS. — The  blackening  of  silver  watches 

als,  &c.  ?  an(j     coingj      in      tjae    vicinity      Of     Sulphur 


HYDROSULPHURIC    ACID.  215 

springs,  is  an  effect  of  hydro-sulphuric  acid  gas.  Its 
discoloring  effect  may  be  illustrated,  by  pouring  a  little 
dilute  sulphuric  acid  upon  a  few  grains  of  sulphuret  of 
iron,  in  a  tea-cup,  and  holding  a  bright  moist  coin  in  the 
fumes.  Its  effect  on  paints  may  be  shown  by  exposing 
a  piece  of  paper,  moistened  with  solution  of  sugar  of 
lead,  in  the  same  manner.  The  white  paper  immedi- 
ately assumes  a  dark  metallic  stain.  Paper  moistened 
with  a  solution  of  tartar  emetic,  takes  a  deep  orange  hue. 
This  experiment  is  often  varied,  by  drawing  amusing 
figures  on  paper,  with  lead  solution,  and  bringing  them 
out  by  exposure  to  the  gas. 

534.  EXPLANATION. — The    change    of 

Explain  the  , 

cause  of  the  color  in  each  case,  is  owing  to  the  forma- 
toior9e°f  tion  of  a  metallic  sulphide,  having  a  diffe- 
rent, and  generally  a  darker  color.  Zinc 
is  not  blackened,  because  its  sulphide  happens  to  be 
white.  For  this  reason,  chemical  laboratories,  and  other 
places  where  hydrosulphuric  acid  is  likely  to  be  evolved, 
should  be  painted  with  zinc  paints,  instead  of  those 
containing  lead. 

535.  RELATIONS  TO  LIFE. — Sulphuretted 

What  is  the 

effect  of  ml-  hydrogen,  if  inhaled  in  any  considerable 
?f  on  ow-  quantity,  acts  as  a  poison.  Caution  should 
therefore  be  observed,  in  experiments  with 
this  gas.  The  mixture  of  gases  which  is  given  off 
from  recently  ignited  coal,  contains  sulphuretted  hy- 
drogen acid,  in  large  proportion,  and  owes  its  deleterious 
qualities,  in  considerable  part,  to  this  admixture. 


216  METALLOIDS. 

AMMONIA. 
536.    DESCRIPTION. — Ammonia  is  a  col- 

WTiat  is  am- 
monia? orless   gas,  of  pungent  smell,  and  alkaline 


Pr°Perties-.    It  is  exhaled  from  vdlcanoes, 
and  is  a  product  of  the  decomposition  of 
all  vegetable  and  animal  matter.     Its  molecule  contains 
one  atom  of  nitrogen  to  three  of  hydrogen. 
mi  . .      .j          537.  PRODUCTION  FROM    ITS   ELEMENTS. 

What  ^s  said 

of  its  produc-  Although  nitrogen  and  hydrogen  gases  are 
trogen°andhy-  the  sole  elements  of  ammonia,  they  cannot, 
drogent  under  ordinary  circumstances,  be  made  to 

unite  directly,  and  form  it.  Heat  does  not  stimulate 
their  affinities  sufficiently  to  bring  about  this  result. 
Electrical  sparks  passed,  for  a  long  time,  through  a 
mixture  of  the  gases,  cause  them  to  combine  to  a  lim- 
ited extent. 

538.    PRODUCTION  FROM  NASCENT  ELE- 

Production 

from  its  nas-  MENTs. — Iron,  at  a  high  temperature,  ex- 
cent  elements.  pelg  hydrogen  from  ordinary  hydrate  of 

potassa,  and  nitrogen  from  nitre.  If  heated  with  both 
together,  it  expels  both  nitrogen  and  hydrogen,  and  the 
two  nascent  elements  unite,  to  form  ammonia.  The 
experiment  may  be  performed  by  covering  bits  of  potash 
and  nitre  with  iron  filings,  and  heating  them  in  a  test- 
tube.  Another  method  of  producing  ammonia,  through 
the  agency  of  platinum  sponge,  is  described  under  the 
head  of  Platinum. 

How  is  ammo-  539t  PREPARATION.— Ammonia  is  com- 
ma common-  monly  made  from  salts  that  contain  it,  by 

ly  prepared  ? 

using  some  strong  base  to  retain  the  acid, 


AMMONIA. 


217 


and  set  the  gas  at  liberty.  Potash  or  lime  may  be 
used  for  this  purpose.  Introduce  into  a  test- 
tube  about  half  an  inch  of  a  stick  of  fused  potash, 
and  covered  it  with  powdered  sal-ammoniac. 
On  the  addition  of  water  to  dissolve  them,  am- 
monia will  be  immediately  evolved.  Rest  the 
tube  on  the  table,  and  place  a  wide-mouthed 
vial  over  it  to  collect  the  gas. 

540.    SOLUTION  IN  WATER. — AQUA  AMVIO- 

How  is  its  so- 
lubility in  wa-  NIA.  Bring  the  mouth  of  the  vial  filled  with 
ter proved?  ammoniacal  gas,  quickly,  into  a  bowl  of 
water.  The  water  will  swallow  up  the  gas  so  rapidly  as 
to  rise  and  fill  the  vial,  producing  a  weak  solution  of 
ammonia,  or  hartshorn.  If  only  a  small  portion  of 
water  be  allowed  to  enter,  and  the  vial  be  then  re- 
moved from  the  bowl  and  shaken,  the  hartshorn  ob- 
tained will  be  comparatively  strong.  For  the  prepira- 
tion  of  the  solution  in  large  quantity,  the  method  given 
in  the  section  on  Chlorine  is  to  be  preferred.  The 
vial  should  be  previously  warmed.  Newly  slaked  lime 
may  be  substituted  for  potash. 

How  ma,,  the  54L       A    MINIATURE      FOUNTAIN.— Fill    a 

ammonia  be      pint  vial  with  ammonia,  by 

employed  to 

produce  a  jet  the  method  above  given,  and 
of  water  ?  immediately  introduce,  air- 
tight, into  its  mouth,  a  moist  paper 
stopper,  with  a  bit  of  pipe-stem  run 
through  it.  Then  invert  the  bottle  into 

O 

a  bowl  of  water.  The  absorption  by 
the  first  portions  of  water  that  enter  will  be  so  com- 

10 


21$  METTALLOIPS. 

plete  as  to  produce  a  vacuum,  into  which  more  wa- 
ter will  rise,  in  a  jet,  as  represented  in' the. figure. 

542.  ALKALINE  PROPERTIES. — Bring  the 

Explain  its 

action  on  material  for  making  ammonia  into  a  tea- 
acids'  cup,  or  similar  open  vessel.  Hold  a  strip 

of  litmus  paper,  previously  reddened  by  an  acid,  in  the 
gas,  as  it  is  evolved.  The  acid  will  be  neutralized  by 
the  ammonia,  and  the  paper  restored  to  its  original  color. 
Any  substance  which  is  very  soluble,  and  neutralizes 
strong  acids,  is  called  an  alkali.  As  ammonia  has  this 
property,  arid  is  also  volatile,  it  is  therefore  called  a  vol- 
atile alkali.  The  same  experiment  with  litmus  paper, 
may  be  also  made  with  the  hartshorn  obtained  in  the 
last  experiment. 

543.          JT    FUMES      WITH    ACID    VAPORS.— 

Describe  its  .  , 

effect  on  acid  Moisten  a  piece  of  paper  with  strong  mu- 
vapors.  riatic  acid,  and  wave  it  to  and  fro  through 

the  gas.  White  fumes  are  produced,  by  the 
union  of  the  muriatic  acid  and  the  ammonia. 
In  uniting,  they  produce  small  particles  of  mu- 
riate of  ammonia,  or  sal-ammoniac,  in  the  air. 
It  is  of  these  that  the  fumes  consist.  It  will 
be  observed,  that  in  this  experiment  the  ma-  j|| 
terial  from  which  the  ammonia  was  originally  pre- 
pared is  reproduced.  The  same  fumes  are  formed, 
on  waving  a  paper  moistened  with  muriatic  acid  through 
the  atmosphere  of  a  stable.  Ammonia  is  constantly 
evolved  in  such  places,  from  the  decomposition  of  ani- 
mal matter. 


PHOSPHURETTED    HYDROGEN.  219 

PHOSPHURETTED  HYDROGEN". 
544.   DESCRIPTION. — Phosphuretted  hy- 

Whatisphos-  .  r  J 

pkurettedky-     drogen  is  a  colorless   gas,  of  an   odor  that 

drogen?  hag  been  compare(i    to    that  Qf  putrid    fish. 

It  is  spontaneously  inflammable  by  contact  with  the 
air.  In  the  relative  proportion  of  its  elements,  it  cor- 
responds with  ammonia.  This  gas  is  sometimes  pro- 
duced in  the  decay  of  vegetable  and  animal  matters. 
The  jack-o-lantern,  or  will-o-t he-wisp,  sometimes  seen 
in  swamps  and  grave-yards,  is  supposed  to  have  its 
origin  in  the  spontaneous  production  and  combustion 
of  this  gas. 

How  is  it  pre-  545.  PREPARATION. — Phosphuretted  hy- 
pared?  drogen  is  made  from  phosphorus,  with  the 

help  of  water  and  an  alkali.  Water  furnishes  the  requi- 
site hydrogen,  if  lime  or  potash  is  at  the  same  time 
present.  Introduce  into  a  small  vial  two-thirds  full  of 
water,  a  stick  of  ordinary  fused  potash,  broken  in  pieces, 
and  a  bit  of  phosphorus  of  the  size  of  a  pea.  On  the 
application  of  heat,  this  gas  is  evolved.  It  is  carried 
through  a  pipe-stem,  and  al- 
lowed to  bubble  up  through 
water  contained  in  a  tea-cup 
or  bowl,  as  represented  in  the 
figure.  If  the  atmosphere  is 
still,  the  bubbles,  as  they  burst 
and  inflame,  form  beautiful 
white  rings,  which  rise  in  succession  into  the  air. 
These  rings  consist  of  particles  of  phosphoric  acid, 
produced  by  the  combustion  of  the  phosphorus  which 


220 


METTALLOIDS. 


is  contained  in  the  gas.  In  order  that  the  gas  may  be 
safely  evolved,  it  is  best  to  heat  the  vial  in  a  tea-cup 
containing  salt,  dissolved  in  three  times  its  bulk  of 
water.  The  addition  of  salt  has  the  effect  of  raising 
the  boiling  point.  The  comparatively  high  tempera- 
ture required,  may  thus  be  obtained  without  exposure 
of  the  vial  to  the  direct  flame  of  a  lamp. 
Explain  the  546.  EXPLANATION. — In  the  action  which 
above  process,  occurs  in  making  phosphuretted  hydrogen 
from  potash,  water,  and  phosphorus,  the  latter  plays 
the  part  of  an  extremely  rapacious  element.  It  makes 
no  distinction  in  the  objects  of  its  appetite,  but  seizes 
upon  both  oxygen  and  hydrogen  of  the  water,  two 
substances  as  widely  different  from  each  other  as  pos- 
sible. It  forms  with  the  one,  phosphuretted  hydrogen, 
and  with  the  other,  what  might  be  called  phosphuret- 
ted oxygen,  but  is,  in  fact,  an  acid.  Potash  is  em- 
ployed in  the  process,  to  promote  the  formation  of  this 
acid.  In  its  absence,  water  resists  the  affinities  of  the 
phosphorus,  and  neither  acid  or  phosphuretted  hydro- 
gen are  obtained. 

COMPOUNDS  OF  HYDROGEN  WITH  CARBON. 

547.  Most  of  the  compounds  of  carbon  and  hydro- 
gen belong  to  the  vegetable  world,  and  will  therefore 
be  more  properly  considered  in  the  chapter  on  organic 
chemistry.  Only  two  of  them,  which  exist  ready 
formed  in  nature,  will  be  here  mentioned. 


CARBURETTED  HYDROGEN. 


LIGHT  CARBURETTED  HYDROGEN. 


What  is  u  kt  '    ^ESCRIPTION-  —  Light   carburetted 

carburctted  hydrogen  is  a  colorless,  inodorous,  in- 
Whcre  does  it  flammable  gas,  about  half  as  heavy  as 
occur?  ajr  jts  moiecule  contains  two  atoms  of 

carbon  to  four  of  hydrogen.  It  is  produced  in  ponds  and 
marshes,  by  the  decomposition  of  vegetable  matter  under 
water,  as  will  be  more  fully  explained  in  Part  III.  From 
this  circumstance  it  is  also  called  marsh  gas.  Mixed 
with  other  gases,  it  issues  from  fissures  in  coal  mines, 
forming  the  fire  damp,  formerly  so  much  dreaded,  on  ac- 
count of  its  explosive  properties.  As  coal  is  of  vegeta- 
ble origin,  the  gas  of  the  mines  which  proceeds  from 
it  is  also  traceable  to  the  vegetable  world.  In  some 
districts,  and  more  particularly  in  regions  where 
borings  are  made  for  salt,  it  issues  from  the  earth  in 
sufficient  quantity  to  form  the  fuel  which  is  required 
to  boil  down  the  brine,  or  even  to  illuminate  villages. 

How  is  it  pre-  549.       PREPARATION.  -  An 

pared?  impure,  light,  carburetted  hy- 

drogen, is  obtained  from  wood,  by  simple 

heating.     For  this  purpose,  saw-dust,  or 

bits  of  shavings  are  heated  in  a  test-tube. 

The  gas  may  be  burned  in  a  jet  as  fast  as 

formed.     The  product    thus    obtained    is 

not    pure,   but  mixed  with    olefiant,  and 

other  gases,  which  make  the  flame  more 

luminous.     The  pure  gas,  may  be  made 

from   strong  vinegar,  (acetic  acid,)  by  the   agency  of 

heat  and  potash,  as  will  be  explained  in  the  latter  part 

of  this  work. 


222  METTALLOIDS. 

550.   EXPLOSIONS  IN  MINES. — Marsh  gas 

Explain  the  .      ,  . 

cause  of  explo-  forms,  with  air,  an  explosive  mixture  be- 
*ion  in  mines?  fore  alluded  ^  which  is  often  the  occa- 

sion  of  fearful  accidents  in  mines.  The  experiment 
may  be  made  with  olefiant  gas,  which  has  the  same 
explosive  property.  This  property  belongs,  indeed,  to 
most  gases  and  vapors  which  contain  hydrogen  ;  as  for 
example,  to  the  vapors  of  ether,  alcohol,  camphene, 
and  "  burning  fluid/' 

551.    DAVY'S  SAFETY  LAMP. — The  dis- 

Descnbe  Da-        .          .  «      •»  -.-i      »•  t       i          •        r-v  -i       •      i 

vy's  safety  tinguished  English  chemist,  Davy,  devised 
lamp.  a  method  Of  security  against  these  explo- 

sions. It  consists  in  surrounding  the 
miners'  lamp  with  wire  gauze,  which 
will  admit  air  through  its  insterstices, 
but  will  not  let  out  flame  to  ignite  the 
explosive  atmosphere  of  the  mine. 
This  effect  may  be  illustrated,  by 
holding  down  a  piece  of  wire  gauze  upon  the  flame  of 
a  candle.  If  the  gauze  is  fine,  the  flame  will  not 
pass  through  it.  This  effect  is  owing  to  the  reduc- 
tion of  temperature  which  the  wire  occasions.  The 
subject  will  be  better  understood  by  reference  to  the 
paragraphs  which  follow,  on  the  nature  of  flame. 


HEAVY  CARBURETTED  HYDROGEN. 

552.  DESCRIPTION. — Heavy  carburetted 

What  are  the  { 

properties  of    hydrogen   is  a  colorless   gas,    of   peculiar 
defiant  gas?     ^ezl\$\\  odor,  also  known  as  olefiant  gas. 


CARBURETTED   HYDROGEN.  223 

It  is  nearly  twice  as  heavy  as  the  light  carburetted  hy- 
drogen just  described,  and  contains  twice  the  quantity 
of  carbon.  It  forms  a  small  proportion  of  the  Jire 
damp,  of  mines,  and  salt  borings,  before  described. 
How  is  it  pre-  553.  PREPARATION. — Heavy  carburetted 
pared?  hydrogen  is  made  from  alcohol,  by  the  de- 

composing action  of  sulphuric  acid.  Bring  into  a  test- 
tube  a  tea-spoonful  of  alcohol,  with  a  little  sand,  and 
add  four  times  as  much  oil  of  vitriol.  On  heating  over 
a  spirit  lamp,  the  gas  is  evolved,  and  may  be  burned 
like  the  gas  just  described,  at  the  mouth  of  the  tube. 
The  acid  employed,  has  the  effect  of  retaining  part  of 
the  elements  of  the  alcohol,  and  allows  the  rest,  to 
escape  as  olefiant  gas.  The  reaction*  is  more  fully  ex- 
plained under  the  head  of  organic  chemistry. 

554.  ILLUMINATING   GAS. — Gas  for   illu- 

How  is  illu- 
minating gas  mination,  is  commonly  prepared  from  bitu- 
minous coal.  Such  coal  is  principally 
composed  of  carbon  and  hydrogen.  A  portion  of 
these  elements,  pass  off  under  the  influence  of  a  high 
temperature,  in  the  form  of  gas.  The  product,  is 
rather,  a  mixture  of  gases,  among  which  light  and 
heavy  carburetted  hydrogen  are  the  principal.  The 
process  may  be  illustrated,  by  heating  a  little  pulver- 
ized bituminous  coal  in  a  test-tube.  If  the  heat  is  in- 
tense, coal  tar  will  be  produced  at  the  same  time.  The 
illuminating  power  of  gas  is  principally  derived  from 
heavy  carburetted  hydrogen.  Its  quality,  within  cer- 
tain limits,  depends  on  the  relative  proportion  of  this 
constituent. 

*  The  term  reaction,  signifies,  in  chemistry,  the  mutual  action   ot 
chemical 


224  METALLOIDS. 

How  is  it  pu-         555.  PURIFICATION.  —  The  gas  as  it  rises, 

rifled  f  contains  ammonia  and  sulphuretted  hydro- 

gen, two  impurities  which  it  is  desirable 

to  remove.     The  first  may  be  stopped 

in  its  passage,  by  a  loose  wad  of  moist- 

ened paper  ;  the  last,  by  a  similar  wad, 

moistened  with  solution  of  sugar  of  lead. 

The  papers  having  been  introduced,  the 

pipe-stem  is  fitted  to  the  tube  with  a  pa- 

per stopper,  and  the  tube  heated  over  the 

alcohol  flame,  with  the   help  of  a  blow-pipe.     When 

the  coal  has  become  red  hot,  the  gas  will   pass  off  in 

sufficient  quantity  to   be  ignited,  at   the  extremity  of 

the  tube. 


How  ore  the  '  ^  ^  conclusion  of  the  process, 

impurities  the  upper  wad  contained  in  the  tube,  will 
be  found  blackened  by  the  sulphuretted 
hydrogen  which  it  has  retained.  On  removing  the 
second  one,  it  will  be  found  to  smell  of  ammonia.  The 
presence  of  this  body  may  also  be  shown,  by  the  fumes 
which  it  yields  with  muriatic  acid. 

557.   ARRANGEMENTS  IN  GAS    WORKS.— 

Describe  the 

process  in  gas  The  process  in  gas  works  is  essentially  the 
same,  as  that  above  described.  The  coal 
is  heated  in  iron  retorts.  The  tar  collects  in  pipes  lead- 
ing from  it.  Carbonate  of  ammonia  is  washed  out  by 
a  jet  of  water,  which  plays  in  an  enlargement  of  the 
pipe.  Lastly,  sulphuretted  hydrogen  is  removed  by 
the  retentive  power  of  a  metallic  base,  lime  being  gen- 
erally substituted  for  lead. 


FLAME.  225 

558.  COLLECTION  AND    DISTRIBUTION. — 
After  purification,  the  gas  is  collected  in 

lectedand  dis-    }™e    n.on    holders,      called     easrmeters. 

tributed  ? 

Tiiese  may  be  represented  by  the  inverted 
tumbler  of  the  figure.     Gas  pouring 
in  from  below  would  lift  and  fill  it.  <^TS^ 

If  an  orifice  were  made  in  the  top, 
the  tumbler  would  immediately  set- 
tle into  the  water.     The  air  would, 
at  the  same  time,  escape  through  the 
orifice.     The  distribution  of  illumina- 
ting gas,  from  public   gas  works,  is  effected  on  the 
same    principle.       The    weight    of    the    sinking    gas- 
ometer, is  sufficient  to  press  it  through  pipes,  to  all  parts 
of  a  large  city. 

559.  GAS  FROM    WOOD. — Gas  may   be 

How  may  gas 

be  made  from  made  from  wood,  by  the  same  means 
above  given.  Only  a  moderate  heat  is  re- 
quired, in  this  case,  to  produce  tar  at  the  same  time. 
Gas  of  higher  illuminating  power  than  that  prepared 
from  wood  or  coal  may  also  be  made  from  oil  fat  or 
rosin.  Even  refuse  vegetable  substance  may  be  em- 
ployed. A  pound  of  dried  grape  skins  have  been  found 
to  yield  350  quarts  of  excellent  illuminating  gas.  The 
dried  flesh  of  animals  has  sometimes  been  employed 
for  its  manufacture. 

FLAME. 

What  is  said  560.  FLAME. — Nothing  in  nature  is,  to 
of  flame  ?  tjie  uninstrilcted  eye,  more  mysterious  than 
flame.  It  is,  seemingly,  body  without  substance,  and 

10* 


226 


METALLOIDS. 


shape,  without  coherence.  It  is  created  by  a  spark, 
and  annihilated  by  a  breath.  Invulnerable  itself,  it 
destroys  whatever  it  touches.  Divided  and  subdivided, 
it  is  still  the  same,  yet  endowed  with  the  power  of  re- 
solving other  materials  into  their  elements.  Chemistry 
resolves  this  mystery,  and  gives  us  the  satisfaction  of 
definite  knowledge  in  its  place.  But,  as  in  all  similar 
case,  while  satisfying  the  understanding,  it  opens  new 
fields  to  the  imagination.  The  subject  of  combustion, 
as  involved  in  flame,  introduces  us,  for  example,  to  a 
knowledge  of  the  grand  system  of  circulation  of  mat- 
ter as  set  forth  in  the  last  chapter  of  this  work. 

561.  STRUCTURE  OF  FLAME. — EXPLANA- 
J5sfa«in  the 

nifitdnre  of      TioN. — Every  lamp  or  candle,  is 

a  gas  factory,  in  which  gas  is  k 
first  produced  out  of  oil  or  fat,  by  the  fire 
which  kindles  it,  and  afterward  by  heat  the 
of  its  own  flame.  A  flame,  if  carefully  ob- 
served, will  be  found  to  consist  of  three 
distinct  parts ;  a  dark  centre,  a  luminous 
body,  and  a  faint  blue  envelop.  The  dark 
centre,  is  unburned  gas.  The  body  of  the 
flame  consists  of  particles  of  carbon  or  lamp- 
black, heated  white  hot,  by  the  combustion 
of  hydrogen.  In  the  exterior  blue  envelop, 
the  carbon  particles  are  consumed  as  they 
are  crowded  outwards,  by  the  flow  of  newly-formed 
gas. 

562.  EFFECT  OF  FLAME   ON   METALS. — 

What  is  the 

effect  of  flame    If  a  tarnished   penny  be  held  perpendicu- 
larly in  the  flame  of  a  lamp  or  candle,  the 


on  metals  ? 


FLAME.  227 

portion  within  the  flame  will  lose  its  coating  of  oxide, 
while  the  exterior  portions  at  the  same  time  become 
more  deeply  oxidized,  and  consequently,  darker  colored. 
It  is  because  there  is  an  excess  of  carbon  arid  hydro- 
gen in  the  interior  of  the  flame,  to  take  oxygen  from 
the  metal,  by  their  superior  affinity,  and  pass  off  with 
it  as  gas  or  vapor.  In  the  outside,  on  the  other  hand, 
there  is  an  abundant  supply  of  air  to  impart  oxygen, 
or,  in  other  words,  to  oxidize.  By  moving  the  coin  to 
and  fro  after  it  is  once  thoroughly  heated,  the  instanta- 
neous conversion  of  metal  into  oxide,  and  oxide  into 
metal,  may  be  readily  observed.  A  beautiful  play  of 
colors,  like  those  upon  a  soap  bubble,  will  be  found  to 
attend  the  transformation.  The  flame  of  a  spirit  lamp 
is,  in  some  respects,  preferable  for  this  experiment. 

563.  OXIDIZING  FLAME. — The  blue  en- 

What  is  the 

oxidizing          velop  of  the  flame,  which,  with  the  hot 
air  adjacent,  has  the  property  of  oxidizing 
metals,  is  called  the  oxidizing  flame. 

564.  REDUCING   FLAME. — The   body  of 
What  ift  the  _J 

reducing  the    flame,  which,    with    the   heated   gas 

flame  ?  within  it,  has  deoxidizing  effects,  and  re- 

duces oxides  again  to  the  metallic  form,  is  called  the 
reducing  flame.  The  process  of  deoxidizing  is  called 
reduction. 

565.    THE  BLOW-PIPE. — The   peculiar 
effects  of  both  the  oxidizing  and  reducing 
simple  con-       flame,  may  be  still  better  obtained,  by  help 

ftructton. 

of  the  simple  mouth  blow-pipe.     In  want 
of  a  metallic  tube,  a  common  tobacco-pipe,  to  the  bowl 


228  METALLOIDS. 

of  which  a  piece  of  a  second  stem  is  fitted, 

as  represented  in  the  figure,  may   be  made 

to   answer    the    purpose.       With    its   aid,  a 

lamp   or    candle  flame  is    converted   into   a 

miniature  blast  furnace.     The  mouth  is  ap- 

plied at  the    end   of  the  long  stem,    while 

the  shorter  one  carries  the  blast  to    the  flame.     The 

orifice   of   the  latter  should   be   extremely  small.     It 

may  be  so   rendered,   by  filling  with  clay,  and  then 

piercing  it  with  a  needle. 

566.  OXIDIZING  BLOW-PIPE  FLAME.  —  To 
d   oxidize    with   the    blow-pipe,    the    flame, 


for  oxidation?    mixed  with  a  large  proportion  of  oxygen, 

Give  an  ex-          .     _  .  .  .. 

ample.  is  blown  forward  upon  the  metal,  or  other 

material,  subjected  to  experiment.  This  is 
effected  by  introducing  the  extremityof  the  blow-pipe, 
a  little  within  the  flame. 
The  air  of  the  lungs  be- 
comes thus  mixed  with 
the  rising  gases.  The 
result  is,  a  slender,  blue 
flame,  at  the  point  of 

which,  within  its  fainter  blue  envelop,  the  metal  is 
to  be  held.  A  piece  of  lead,  of  the  size  of  a  grain  of 
wheat,  placed  on  charcoal,  hollowed  out  for  the  purpose, 
and  exposed  to  the  flame,  will  soon  bo  converted  into 
litharge.  The  oxide  will  be  recognized  by  the  yellow 
incrustation  which  it  forms  upon  the  charcoal  support 
567.  REDUCING  BLOW-PIPE  FLAME.  —  To 

How  is  the 

blow-pipe  used   convert   oxides    into   metals,   or    in    other 


blow-pipe,    the    gases  of   the   flames   are 


FLAME. 


229 


blown  forward,  upon  the  substance,  mixed  with  little 
air.  The  extremity  of 
the  blow-pipe  is  placed 
against  the  outer  wall  of 
the  flame,  a  little  higher 
than  in  the  previous  case. 
The  flame  thus  produced 
is  yellow,  and  of  the  shape  represented  in  the  figure. 
The  oxide  to  be  reduced,  is  to  be  placed  within  the 
yellow  body  of  the  flame,  but  near  its  termination. 
The  litharge  produced  in  the  last  experiment,  may 
be  re-converted,  by  this  means,  into  metallic  lead. 
568.  OXYHYDHOGEN  BLOW-PIPE. — The 

Describe  the      compound    or   oxhydrogen    blow-pipe,    as 

oxyhydrogc* 

blow-pipe.          commonly   constructed,    consists    of    two 

gasometers,  containing,  the  one,  oxygen, 
and  the  other  hy- 
drogen gas.  Tubes 
leading  from  these, 
are  brought  together 
at  their  extremity, 
and  the  two  gases  are 
burned  in  a  single  jet. 
The  heat  thus  pro- 
duced, is  the  most  in- 
tense that  has  ever 
been  realized  except 
by  galvanic  means.  Iron,  copper,  zinc,  and  other  metals, 
melt  and  bum  in  it  readily  ;  the  former,  with  beau- 
tiful scintillations,  and  the  latter,  with  characteristic 
colored  flames.  With  a  sufficiently  constant  flame 

10* 


230 


METALLOIDS. 


platinum  also  may  be  readily  fused.  The  apparatus 
represented  in  the  figure,  furnishes  a  simpler  means  of 
obtaining  similar  results/  An  abundant  flow  of  hy- 
drogen is  required,  and  a  pint  bottle  should,  therefore, 
be  employed  in  its  preparation.  To  retain  it  free  from 
water,  which  would  tend  to  reduce  the  heat  of  the 
flame,  a  little  cotton  may  be  introduced  into  the  bowl 
of  the  pipe  through  which  it  passes.  In  evolving  the 
oxygen,  only  a  part  of  the  tube  should  be  heated  at  a 
time,  lest  the  gas  should  be  too  rapidly  evolved. 

FLAME  CONTINUED. — The  student  will 
ture  of  flame  already  have  found  abundant  evidence  that 
{rai«rf£  UlU8~  air  or  oxygen  *s  essential  to  combustion. 
A  still  more  striking  illustration  of  the  sub- 
ject remains  to  be  given.  A  phosphorus 
match,  if  suddenly  introduced  into  the 
interior  of  a  flame,  notwithstanding  the 
high  temperature  in  its  vicinity,  is  not 
ignited.  The  wood  burns  off,  but  the 
phosphorus  of  the  match  does  not  un- 
dergo combustion.  The  same  principle 
may  be  illustrated  by  holding  a  match 
for  a  moment  through  the  body  of  the 
flame.  It  is  consumed  at  the  sides, 
while  the  centre  remains  unburned. 


CLASSIFICATION    OF    METAI-3.  231 

CHAPTER  II. 

METALS. 

569.  CLASSIFICATION. — The  metals  may 

How  may  the 

metals  be  das-  be  arranged  in  groups,  or  classes,  according 
to  their  affinity  for  oxygen.  Those  which 
tarnish,  or  rust  most  readily,  come  first  in  order,  while 
the  last  group  is  made  up  of  the  noble  metals,  which 
retain  their  brilliancy,  unimpaired. 

570.  CLASS  i.     POTASSIUM   AND  SODIUM. 

Describe  the 

metal*  of  These  two  metals  combine  with  oxygen  so 
eagerly,  as  to  tarnish  instantaneously,  on 
exposure  to  the  air.  They  even  seize  on  that  which 
is  contained  in  water  and  expel  its  hydrogen.  The 
hypothetical  metal,  ammonium,  is  described  in  connec- 
tion with  this  group,  because  of  the  similar  properties 
of  its  compounds. 

Describe  Class        571.    CLASS  II.    BARIUM,  STRONTIUM,  CALCI- 

IL  UM,  MAGNESIUM. — The  metals  of  this  class 

show  their  affinity  for  oxygen,  in  the  same  manner  as 
those  of  Class  I.  But  they  are  inferior,  in  this  respect,  to 
both  potassium  and  sodium.  Either  of  these  metals 
can  deprive  them  of  the  oxygen  with  which  they  may 
have  combined. 

Describe  Class  572.  CLASS  III.  MANGANESE,  ALUMINIUM, 
IIL  IRON,  CHROMIUM,  COBALT,  NICKEL. The 

metals  of  this  class  tarnish  less  rapidly  than  the  fore- 
going, by  exposure  to  the  air.  In  order  that  they  may 
decompose  water,  and  appropriate  its  oxygen,  they  re- 


232  METALS. 

quire  the  stimulus  of  an  acid,  or  of  heat.  Except  in 
the  case  of  manganese,  the  heat  must  be  sufficient  to 
convert  the  water  into  steam.  Strictly  speaking,  there- 
fore, they  do  not  decompose  water,  but  steam. 

Describe  Class  5?3.     CLASS  IV.       TlN    AND      ANTIMONY.—- 

IV-  Tin  and  antimony  tarnish  less  readily  than 

the  metals  of  the  previous  class.  To  enable  them  to 
decompose  water,  and  appropriate  its  oxygen,  they  re- 
quire the  stimulus  of  a  red  heat.  An  acid,  or  mode- 
rate heat  will  not  suffice. 

Describe  Class  ^74.      CLASS   V.     COPPER,     BISMUTH,      AND 

LEAD. — Although  copper  and  lead  become 
tarnished,  or  covered  with  a  thin  film  of  oxide,  rather 
more  readily  than  the  metals  of  the  last  two  groups, 
their  affinity  for  oxygen  under  other  circumstances  is 
less.  This  is  evident  in  the  fact  that  a  red  heat  ena- 
bles them  to  decompose  water  and  appropriate  its  oxy- 
gen, but  feebly.  Acids  will  not  suffice.  Bismuth 
does  not  tarnish  so  readily  as  copper  or  lead. 

Describe  Class  5?5.    CLASS  VI.    MERCURY,     SILVER,     PLA- 

VL  TINUM,    AND    GOLD. — The    metals   of    this 

class  do  not  tarnish,  and  do  not  decompose  water  under 
any  circumstances.  Even  if  made  to  combine  with 
oxygen  by  other  means,  they  yield  it  again  very  readily, 
and  return  to  the  condition  of  metals.  They  are  called 
the  noble  metals. 


POTASSIUM.  233 

CLASS  I. 

POTASSIUM. 
576.     DESCRIPTION.  —  Potassium    is    a 

bluish     White     metal>     Hghter    than    Water> 


solvents;          and  soft,  like  bees-wax.     Like  wax.  it  is 

occurrence? 

also  converted  by  the  heat  of  an  ordinary 
fire  into  vapor.  Water  and  acids  dissolve  it  readily. 
The  metals  of  this  and  the  folloAving  groups,  were  dis- 
covered by  Sir  Humphrey  Davy,  early  in  the  present 
century.  They  were  first  produced  by  the  galvanic 
process.  Potassium  is  a  constituent  of  many  rocks, 
of  all  fertile  soils,  and  of  the  ashes  of  plants.  The 
more  important  minerals  which  contain  it,  are  men- 
tioned in  Chapter  III. 

577.   PREPARATION.  —  Potassium  is  made 

flow  is  potas- 

sium pre-          from    carbonate   of    potassa,  by  removing 
pared?  jtg  carbolu'c  acid  and  ox- 

ygen. This  is  accomplished  by 
heating  intensely  with  charcoal,  which 
removes  both  in  the  form  of  carbonic  oxide. 
The  metal  which  accompanies  the  gas,  in  the  form 
of  vapor,  is  condensed  by  naptha,  instead  of  water. 
The  process  is  essentially  the  same  as  that  for  preparing 
phosphorus,  but  requires  apparatus  beyond  the  reach  of 
the  ordinary  experimenter.  Cream  of  tartar,  if  heated, 
is  converted  into  a  nearly  suitable  mixture  of  carbonate 
of  potassa,  and  pure  carbon,  for  this  purpose.  A  small 
quantity  of  charcoal,  in  fragments,  is  added,  and  the 
whole  heated  intensely  in  an  iron  retort. 


234 


METALS. 


Explain  the  578.        COMBUSTION   ON     WATER. PotaS- 

actionofpo-       gmm     jf  thrown      UDOll 
tassium  on  r 

water.  water,    is   immediately 

ignited  and  burns  with  a  beautiful 
violet  flame.  Strictly  speaking,  it  is  not  potassium 
which  burns,  but  the  hydrogen  which  it  sets  at  liberty, 
Owing  to  its  strong  affinity  for  oxygen,  it  takes  this 
element  from  water,  liberating,  and  at  the  same  time 
kindling,  the  hydrogen  with  which  it  was  before 
combined.  The  color  of  the  flame  is  due  to  a  small 
portion  of  vaporized  potassium  which  burns  with 
this  gas,  as  it  is  evolved.  The  globule  of  metal  used 
in  this  experiment,  gradually  disappears,  because  the 
potassa  which  it  forms  by  uniting  with  oxygen,  is 
soluble  in  water. 

579.    USES  OF   POTASSIUM. — Potassium 
State  the  uses 

of  potassi-  has  not  been  applied  to  important  uses  in 
the  arts,  but  is  a  valuable  agent  in  the 
hands  of  the  chemist.  It  is  a  key  which  unlocks 
many  substances  from  the  prison  in  which  nature  has 
confined  them.  Through  its  agency,  brilliant  metals 
may  be  obtained  from  lime,  magnesia,  and  common 
clay. 

580.  This  effect  depends  on  the  supe- 

On  what  does 

its  action  dc-  nor  affinities  of  potassium,  which  enable 
pcnd?  -t  to  appr0pr{ate  oxygen,  chlorine,  and 

other  substances,  with  which  the  above,  and  several 
other  metals  are  combined  in  nature,  and  to  isolate  the 
metals  themselves.  The  potassium  is,  at  the  same 
time,  converted  into  oxide,  or  chloride  of  potassium, 


SODIUM.  235 

which  is  soluble  in  water,  and  may  be  washed  away 
from  the  metal  which  has  been  produced. 

SODIUM. 

581.  PROPERTIES. — The  metal  sodium  is 

Sodium — de- 
scription, similar  in  its    properties  to   potassium.      It 

^dvni^and  *s  PrePared  by  similar  means,  from  carbo- 
occurrcnce?  nate  of  soda,  and  may  be  employed  by  the 
chemist,  for  the  same  purpose.  It  occurs,  principally, 
in  nature,  in  the  form  of  common  salt.  Thrown  upon 
water,  it  decomposes  it,  without  however  igniting  the 
hydrogen  which  is  evolved.*  Sodium  is  readily  sol- 
uble either  in  water  or  acids. 

582.  USES  OF  SODIUM. — Sodium  is  now 

.For  K'hat  pur-  . 

pose  is  it  prepared  in   large   quantities,    in    France, 

as  a  material  to  be  used  in  the  manu- 
acture  of  the  metal  aluminiu  n.  Its  cost,  a  few  years 
since,  was  ten  dollars  an  ounce.  It  can  now  be  pro- 
cured for  less  than  a  dollar  per  pound. 

AMMONIUM. 

583.  Ammonium  is  a  compound  of  ni- 

Wkat  is  said  .          . 

of  ammoni-  trogen  and  hydrogen,  which  is  presumed 
um'  to  be  a  metal.  Its  molecule  contains  one 

atom  of  nitrogen,  to  four  of  hydrogen.  If  a  metal,  it 
differs  from  all  others,  in  being  a  compound,  and  not  a 
simple  element.  There  are,  however,  good  grounds 

*  If  sodium  is  wrapped  in  paper,  to  prevent  waste  of  heat,  it  burns 
with  flame,  like  potassium,  upon  water. 


236  METALS* 

for  believing  in  the  existence  of  such  a  compound 
gaseous  metal.  The  chloride  of  ammonium  is  named 
in  accordance  with  this  view.  Judging  from  the  prop- 
erties of  the  salt,  we  might  reasonably  expect,  by  re- 
moval of  its  chlorine,  to  obtain  from  it  a  substance 
with  metallic  properties,  as  well  as  from  chloride  of 
sodium  or  common  salt.  But  the  experiment  does  not 
justify  the  expectation.  As  soon  as  the  chlorine  is  re- 
moved, the  metal  also  decomposes,  and  a  mixture  of 
gases  is  the  result.  The  principal  ground  for  attribu- 
ting a  metallic  character  to  the  combination  of  nitrogen 
and  hydrogen  gases,  in  the  preparations  above  stated, 
has  been  already  indicated.  They  supply,  in  certain 
salts,  the  place  which  known  metals  fill  in  the  other 
and  similar  compounds.  A  confirmatory  experiment 
is  described  in  the  succeeding  paragraphs. 

584.      AMMONIUM     AMALGAM. — Another 

Slate  another  ....,  .  ~ 

reason  for  be-  ground  for  believing  in  the  existence  of 
lexScelofea  ammonium,  with  true  metallic  properties, 
metal  ammo-  is  found  in  the  following  experiment :  If 

nium.  „  .  •        i        •  i 

chloride  of  ammonium  be  mixed  with  an 
amalgam  of  sodium  and  mercury,  a  double 
decomposition  ensues.  The  chlorine  and 
sodium  unite  to  form  common  salt,  while  the 
mercury  combines  with  the  ammonium  with- 
out losing  its  metallic  lustre.  But  there  is  no 
instance  of  this  retention  of  metallic  properties  in  the 
combination  of  mercury  or  any  other  metal  with  any 
non-metallic  substance.  The  inference  is  that  ammo- 
nium is  a  metal.  But  any  attempt  to  isolate  it  by  re- 


BARIUM. 


237 


moval  of  the  mercury  from  the  amalgam,  is  ineffectual. 
As  soon  as  this  is  done  the  ammonium  is  resolved  into 
gaseous  ammonia  and  hydrogen.  This  change  takes 
place,  indeed,  spontaneously. 

585.  In  performing  the  above  experiment, 

How  is  the 

amalgam  ex-  a  small  globule  of  potassium  or  sodium  is 
formldl  peT~  heated  with  a  thimble  full  of  mercury  in  a 
test-tube,  and  a  strong  solution  of  sal  am- 
moniac added.  The  mercury  increases  in  bulk  without 
losing  its  lustre,  and  continues  to  expand  till  it  fills  the 
tube  or  glass  with  a  light  pasty  amalgam. 

CLASS  II. 

BARIUM,  STRONTIUM,  CALCIUM,  MAGNESIUM. 

586.  BARIUM.  —  Barium  is  a  soft  silvery 


pro-    metal,   easily  tarnished  in  the   air.     It  is 
ami       made  from  baryta,  by  the  process  already 
described   under   the   head    of   potassium. 
Its  compounds,  including  baryta,  from  which  it  is  pre- 
pared, are  hereafter  described.     Barium  is  soluble   in 
water  and  most  acids. 

587.  STRONTIUM.  —  Strontium    is   very 

Strontium  —  „  . 

description,       similar  to  barium,  but  darker  in  color.    It  is 

absolvents?     Produced  from  strontia  by  a  similar  process. 

Its  solvents  are  also  the  same. 

588.  CALCIUM.  —  The   metal   calcium  is 

Calcium  —  de-         .  . 

pro-    similar  to  barium,  and  is  made  from  lime 
b>"  the    use   of  Potassium,   as  before   de- 
scribed.    Its  solvents  are  the  same  as  those 
of  the  metals  above-named. 


238 


METALS. 


Magnesium-  589'    MAGNESIUM.— Magnesium  is  a  Soft 

description,       white  metal,   prepared   from    its    chloride 

preparation,        ,  .  . 

solvents  and  instead  oi  the  oxide,  by  similar  means. 
None  of  the  metals  of  this  class  have  as  yet 
been  applied  to  any  useful  purpose  in  the  arts.  Water 
oxidizes  magnesium  as  it  does  the  other  metals  of  the 
class,  but  converts  it  into  an  insoluble  white  powder. 
Most  acids  dissolve  it. 


CLASS  III. 

ALUMINIUM 

590.     DESCRIPTION. — Aluminium    is  a 
bluish   white  metal,   made  from  common 
currence,  and     cjay.     It  is  about    one-third  as  heavy  as 

solvents  ?  *  y 

iron.  It  fuses  at  the  same  temperature 
as  silver,  and  preserves  an  untarnished  surface  in  the 
air.  It  does  not  decompose  water,  even  with  the  aid 
of  boiling  heat.  Alloyed  with  iron,  it  protects  the 
latter  from  the  action  of  the  air.  This  metal  is  a  con- 
stituent of  common  clay,  and  therefore  a  part  of  all  fer- 
tile soils  and  the  rocks  that  produce  them.  It  is  also 
a  constituent  of  numerous  minerals.  By  its  discovery 
every  clay  bank  is  converted  into  a  mine  of  precious 
metal. 

How  is  it  pre-  591.  PREPARATION. — Aluminium  is  pre- 
pared? pared  like  magnesium,  from  its  chloride, 
by  fusion  with  potassium  or  sodium.  The  latter  rnetal 
is  commonly  employed.  The  fluoride  may  also  be 
used  in  the  process,  or  the  mineral  cryolite,  which 


MANGANESE.  239 

is  a  compound  of  fluoride  of  aluminium  with  fluoride  of 
potassium.  The  latter  constituent  interferes  in  no  wise 
with  the  process.  The  method  of  preparing  the  chlo- 
ride, as  a  material  for  the  production  of  the  metal,  is 
given  in  the  section  on  Chlorides. 

592.  ACTION  OF  ACIDS. — Muriatic  acid 

What  is  the  . 

action  of  acids  is  its  proper  solvent,  and  forms  with  it  a 
colorless  solution.  Nitric  acid  whitens  it, 
if  previously  dipped  into  strong  potash  or  soda.  Dilute 
sulphuric  acid  is  without  action.  Aluminium  may  be 
poured  from  one  vessel  to  another  in  a  fused  condition 
without  oxidation.  Like  silver  it  may  be  deposited  by 
the  galvanic  process. 

593.  It  is  highly  sonorous,  and  therefore 
other  proper-     adapted  to    manufacture  of  bells.      This 

metal  is  now  prepared  in  France  at  less 
than  three  dollars  per  pound.  The  French  government 
propose  to  use  it  for  helmets  and  cuirasses,  for  which 
it  is  especially  fitted  by  its  lightness  and  tenacity. 

594.  MANGANESE. — Manganese  is  a 
description,  grey  brittle  metal,  produced  from  its  oxide 
production,  b  heatnig  wjth  charcoal.  It  is  found  in 

occurrence, 

solvents  and  nature  as  black  oxide  of  manganese  and  as 
a  constituent  of  many  other  minerals.  It 
enters  also  in  small  proportions  into  the  composition  of 
soils.  Diluted  sulphuric  or  muriatic  acid  are  its  proper 
solvents,  forming  with  it  pale  rose-colored  solutions. 
The  black  oxide  serves  as  a  source  of  oxygen,  and  is 
also  employed  in  the  preparation  of  chlorine  gas.  It  is 
also  used  in  the  production  of  artificial  amethysts,  and 
also  to  impart  to  glass  the  same  violet  tint. 


240  METALS. 

CLASS  III. 

IRON. 
595.  DESCRIPTION. — Pare  iron  is  nearly 

Mention  some 

properties  of  white,  quite  soft,  exceedingly  malleable 
and  highly  tenacious.  It  may  be  rolled 
into  leaves  so  thin  that  a  bound  book  containing  forty- 
four  such  leaves  shall  be  only  one-fifteenth  part  of  an 
inch  in  thicknesss.  In  the  condition  of  perfect  purity 
it  is  never  seen  except  in  the  chemist's  laboratory. 
Even  the  purest  iron  of  commerce  contains  traces 
of  other  substances.  Dilute  sulphuric  or 
muriatic  acids  are  its  proper  solvents,  form- 
ing with  it  green  solutions.  The  addition 
of  nitric  acid,  or  chlorine,  changes  the  color 
to  red.  Iron  may  be  readily  burned,  as  has  al- 
ready been  shown  in  the  section  on  Oxygen. 

596.      OCCURRENCE. — Iron    is   a   most 

Does  metallic  . 

iron  occur  in  abundant  metal,  but  is  rarely  or  never 
nature?  found  in  the  metallic  form,  excepting  as 

meteoric  iron.  In  this  condition  it  is  always  alloyed 
with  nickel.  The  latter  metal  being  uniformly  com- 
bined with  it  in  masses  known  to  have  fallen  to  the 
earth  as  meteors,  its  presence  in  similar  masses  dis- 
covered on  the  surface  of  the  earth,  is  regarded  as  evi- 
dence of  their  meteoric  origin.  Iron  is  a  constituent 
of  a  great  variety  of  minerals,  of  all  soils  and  plants, 
and  even  of  the  blood  of  animals.  The  peroxide  of 
iron,  the  magnetic  oxide,  and  clay  iron  stone,  are  its 
principal  ores.  Whole  mountains  of  the  magnetic  oxide 
exist  in  Missouri,  and  in  Sweden. 


IRON. 


241 


How  is  iron 
produced  ? 


597.  PRODUCTION. — Iron  is  produced 
from  its  ores,  which  are  impure  oxides,  by 
heating  with  lime,  to  remove 
the  impurity ;  and  at  the 
same  time  with  coal,  and 
the  gases  proceeding  from  it, 
to  remove  the  oxygen.  A 
smelting  furnace,  such  as  is 
represented  in  the  figure, 
being  previously  heated,  is 
charged  with  the  material  in 
layers,  and  the  heat  main- 
tained by  the  coal  of  the 
mixture.  In  the  upper  part 
of  the  furnace  the  materials 

are    thoroughly    dried.       As 

they    gradually    settle,    they 

become  more  thoroughly  heated,  and  meet  carbonic 
oxide  from  the  coal  below,  which  robs  the  iron  of  its 
oxygen,  and  converts  it  into  particles  of  metal.  Still 
lower  down,  the  lime  combines  with  the  earthy  por- 
tions of  the  ore,  forming  a  liquid  glass.  The  re- 
duced iron  thus  liberated,  collects,  fuses,  arid  sinks  to 
the  bottom  of  the  furnace.  Prom  this  point  it  is  run 
off  into  channels  of  sand,  where  it  hardens  into  pig 
iron. 

How  is  the  598.   EXPLANATION. — The  ordinary  im- 

slag  formed?     purities  of  the  ore-  are   clay  and  quartz,  or 

For  what  uses     r  j  T.  ? 

may  it  be  em-  silica.  Lime  has  the  property  of  forming, 
p  oye  with  both  of  these,  a  fusible  glass,  or  slag, 

which  floats  upon   the  melted  iron.     This  material  is 

11 


242 


METALS. 


of  a  light  green  color.  But  it  may  be  otherwise  col- 
ored to  suit  the  taste,  and  cast  into  slabs,  columns,  ar- 
chitectural and  parlor  ornaments  of  great  beauty. 
The  process  by  which  its  brittleness  is  removed,  and 
the  slag  adapted  to  the  above  uses,  has  not  been  made 
public. 

599.  CAST  IRON — The  pig   or  cast  iron, 

Give  the  com-  .     . 

position  and     as  it  is  called,  which  is  thus  obtained  from 

PcraTiron°f       the  furnace>  is    not    Pure    iron>  but    a   con> 

pound  of  iron  with  carbon.  It  has  ob- 
tained four  or  five  per  cent,  of  this  element  from  the 
coal  with  which  it  was  reduced.  The  addition  of 
carbon  to  its  composition  causes  iron  to  melt  more 
readily.  But  for  its  absorption,  the  metal  would  not 
have  become  sufficiently  soft  to  flow  from  the  fur- 
nace. Carbon  has  also  the  opposite  property  of  mak- 
ing iron  harder  and  more  brittle  when  cold.  Castings 
of  agricultural  implements  and  other  objects,  are  made 
by  remelting  the  pig  iron,  and  pouring  it  into  moulds 
of  the  required  shape. 

600.  WROUGHT  IRON. — Wrought  iron  is 

How  is 

wrought  iron  made  from  cast  iron,  by  burning  out  its 
made?  carbon.  This  done  in  what  is  called  a 

reverberatory  furnace,  such 
as  is  represented  in  the  fig- 
ure. The  carbon  is  burned 
out  by  the  surplus  air  of  the 
flame,  which  is  made  to  play 
upon  the  molten  iron.  Prom 
the  constant  stirring  which  is  essential,  such  a  furnace 
for  refining  iron  is  called  a  puddling  furnace.  The 


IRON.  243 

metal  becomes  stiffer  as  it  loses  carbon,  and  is  then 
hammered  and  rolled  into  bars. 

601.  IRON  WIRE. — The  bar.  or  wrought 

Mention  an 

important         iron  thus  produced,  is  highly  malleable  and 

wrought  iL.     ductile>  aild  ma7  be  rolled  into  sheets,  or 
How  i$  iron       drawn  into  the  finest  wire.     Wire  is  made 

wire  made  ? 

by  drawing  a  wrought  iron  bar,  by  ma- 
chinery, through  a  hole  of  less  than  its  own  diameter, 
and  repeating  the  process  until  the  required  degree  of 
fineness  is  attained.  Wrought  iron  loses  its  tenacity, 
and  becomes  granular  and  brittle,  like  cast  iron,  by  long 
jarring.  This  effect  sometimes  occurs  in  the  wheels 
and  axles  of  railway  carriages,  and  is  the  occasion  of 
serious  accidents. 

602.  WELDING. — Wrought  iron  becomes 

How  is 

wrought  iron  soft  at  a  certain  heat,  without  melting. 
This  property,  which  adds  greatly  to  its 
usefulness,  belongs  to  no  other  metal  excepting  plati- 
num. In  the  soft  state,  two  pieces  may  be  united  by 
hammering.  This  process  is  called  welding.  The 
surfaces  to  be  welded  are  sprinkled  with  borax,  to  pro- 
tect them  from  the  air,  which  would  form  a  crust  of 
oxide  of  iron,  and  prevent  a  perfect  contact.  Its  fur- 
ther action  is  explained  in  the  chapter  on  Salts.  Beside 
borax,  other  materials  having  a  similar  effect  are  fre- 
quently employed. 

How  is  steel  603.  STEEL. — Steel  may  be  made  from 
made  ?  cast  iron  by  burning  out  half  its  carbon. 

Or  it  may  be  made  from  wrought  iron,  by  return- 
ing half  of  the  carbon  which  was  removed  in  its 
preparation.  The  latter  is  the  process  generally  pur- 


244 


METALS. 


sued.  It  consists  in  burying  the  wrought  metal  in 
iron  boxes  containing  charcoal,  and  heating  it  for 
several  days,  till  combination  with  a  certain  portion 
of  the  carbon  is  effected. 

604.     ANNEALING. — The    hardness  of 

How  is  steel  .  ..... 

made  soft  or  steel  depends  upon  the  rate  at  which  it  is 
cooled.  By  heating  it  to  redness,  and 
cooling  it  slowly,  it  is  rendered  as  soft  and  malleable  as 
wrought  iron.  This  process  is  called  annealing.  By 
cooling  it  very  suddenly,  it  becomes  as  hard  and  brittle 
as  cast  iron.  Steel  instruments  are  commonly  ham- 
mered out  of  the  soft  steel,  and  subsequently  hardened. 
How  is  steel  605.  TEMPERING  STEEL. — Steel  hardened 

tempered?  as  above  described  is  too  hard  and  brittle 
for  most  uses.  Any  portion  of  its  original  softness  and 
tenacity  may  be  returned  to  it,  by  reheating  and  slow 
cooling.  To  restore  the  whole,  a  red  heat  would  be 
required.  To  give  back  part,  and  make  a  steel  so 
tough  as  not  to  break  readily,  yet  sufficiently  hard  for 
cutting,  a  lower  temperature  is  employed.  This  process 
is  called  tempering.  The  sort  of  temper  imparted  de- 
pends upon  the  degree  of  heat  which  has  been  em- 
ployed. 

606.  The  proper  temperature  is  ascertained 

How  is  the  ,  .   ,      ,  , 

proper  heat       by  the  color  which  the  steel  assumes  when 

ascertained?       heated<       Toolg  for  cutting  metal  are  heated 

till  they  become  a  pale  yellow  ;  planes  and  knives,  to 
a  darker  yellow  ;  chisels  and  hatchets,  to  a  purplish 
yellow  ;  springs,  till  they  become  purple,  or  blue.  In 
each  case  they  are  afterward  slowly  cooled.  These 
colors  are  owing  to  a  film  of  oxide  of  iron,  which  is 


CHROMIUM. 


245 


formed  upon  the  steel  under  the  influence  of  heat.  The 
tint  is  different,  according  to  the  thickness  of  the 
film.  All  these  colors  may  be  seen  by  heating  a  knit- 
ting-needle in  the  flame  of  a  spirit  lamp.  Where  it  is 
hottest  it  becomes  blue,  and  this  color  shades  off  into 
pale  yellow  on  either  side,  like  the  colors  of  the  solar 
spectrum. 


Chromium  — 


CHROMIUM. 
607.  DESCRIPTION.  —  Chromium  is  a  grey 

.  * 

description,       metal,  not  readily  tarnished,   and  so  hard 

Po™f"so!™nts,      aS  t0  SCratch  glass'       Jt    is  of  no  use  in  the 

and  uses?  arts  in  the  metallic  form.  It  is  found  in 
combination  with  iron,  as  chromic  iron,  and  also  in 
beautiful  Crystals,  as  red  chromate  of  lead.  It  may  be 
prepared  from  its  oxide,  like  iron,  by  heating  with 
charcoal.  Its  compounds  are  much  used  as  paints. 
Chrome  green  and  chrome  yellow  are  among  the 
number.  Its  proper  solvents  are  the  same  as  those  of 
iron.  The  solutions  of  this  metal  are  green. 


COBALT 

608.  DESCRIPTION. — Cobalt  is  another 
grey  metal,  tarnishing  but  slightly  in  the 
air.  It  is  somewhat  malleable.  It  is  found 
combined  with  arsenic,  as  arsenical  cobalt, 
and  in  some  other  minerals.  As  metal, 
it  is  without  useful  application  in  the  arts.  It  may 
be  produced  like  iron,  by  heating  with  charcoal, 


Cobalt— de- 
scription, pro- 
duction, oc- 
currence, sol- 
vents, and 
uses  ? 


246  METALS. 

but  is  more  readily  reduced  by  hydrogen.  A  cur- 
rent of  this  gas  being  made  to  pass  through  a  hot 
tube  containing  the  oxide,  it  combines  with  oxygen, 
and  passes  off  with  it  as  water,  leaving  the  metal  in  the 
form  of  a  fine  powder.  Its  proper  solvents  are  the 
same  as  those  of  iron  and  chromium.  The  solutions 
of  cobalt  are  pink.  The  oxide  is  employed  for  im- 
parting a  blue  color  to  glass. 

NICKEL. 

Nickel—  609.  Nickel  is  still  another  grey  metal, 

'       l[8hiQ*  in  color  and  more  malleable  than 


ores,  solvents,     cobalt,  and  not  much  affected  by  the  air. 

and  uses?  •*     •     *          i   •  i  •         •  •  «    " 

It  is  round  in  combination  with  copper,  in 
the  mineral  called  copper  nickel.  It  may  be  prepared 
by  either  of  the  methods  used  for  cobalt.  Its  proper  sol- 
vents are  the  same  as  those  of  the  last  four  metals.  The 
solutions  of  this  metal  are  green.  Nickel  is  principally 
used  in  the  preparation  of  the  alloy  called  German  sil- 
ver. This  imitation  of  silver  is  brass  rendered  white 
by  the  proportion  of  nickel  which  it  contains.  The 
alloy  is  composed  of  one  hundred  parts  of  copper,  six- 
ty of  zinc,  and  forty  of  nickel. 


ZINC. 
610.     DESCRIPTION. — Zinc  is  a  bluish- 

— de- 
scription,         white  metal,  readily  tarnished  in  the  air. 

Jt  is  brittle  at  ordinary  temperatures,  and 
converted  into  vapor  at  a  red  heat.     If 


ZINC.  247 

heated  somewhat  above  the  temperature  of  boiling  wa- 
ter, it  can  be  rolled  into  sheets.  At  a  higher  tempera- 
ture it  again  becomes  brittle.  Sulphuric  and  muriatic 
acids  dissolve  it  readily,  forming  colorless  solutions. 
It  is  not  found  native.  The  red  oxide,  and  the  carbon- 
ate, called  calamine,  are  among  its  more  important  ores. 
611.  PRODUCTION.  —  Zinc  is  produced 
produced?  from  its  oxide  by  heating  with  charcoal  to 


remove  tne  oxygen?  or>  m  other  words,  to 
reduce  it.  When  made  from  the  carbonate, 
the  ore  is  previously  roasted,  to  expel 
its  carbonic  acid  and  bring  it  to  the 
state  of  oxide.  As  the  metal  is  volatile 
at  the  heat  required  in  its  reduction,  an 
ordinary  furnace,  such  as  is  used  for  making  iron,  can- 
not be  employed  in  the  process  :  the  metal  would  be 
lost  in  vapor.  A  clay  retort,  or  muffle,  such  as  is  re- 
presented in  the  figure,  is  used  instead.  The  zinc  va- 
por condenses  in  the  cool  neck,  and  falls,  in  drops  of 
melted  metaLinto  a  vessel  of  water  placed  to  receive 
it.  The  carbonic  oxide  produced  in  the  process  at  the 
same  time,  escapes  into  the  air.  It  will  be  observed, 
that  the  process  is  essentially  the  same  as  that  for  pro- 
ducing potassium  and  phosphorus,  as  before  described. 
Acids  dissolve  zinc,  forming  colorless  solutions. 

612.  ACTION  OF  HEAT  AND  AIR.  —  Zinc 

How  may  zinc  -:- 

be  burned?  may  be  burned  by  heating  it  on  charcoal, 
in  the  blow-pipe  flame.  It  melts,  and  con- 
verts itself  rapidly  in  the  process  into 
white  oxide  of  zinc.  If  an  intense 
heat  is  employed,  the  vapors  of  the 
metal  burst  through  the  crust  and  burn 


248  METALS. 

to  oxide,  with  a  brilliant  greenish  flame.  When  zinc 
is  burned  in  considerable  quantity,  in  a  highly  heated 
crucible,  the  oxide  forms  flakes  in  the  air,  to  which  the 
name  of  lana  philosophica,  or  philosophers'  wool,  was 
given  by  the  alchemists.  The  metal  may  be  melted 
over  a  spirit  lamp,  in  an  iron  spoon. 
Mention  the  613.  USES  OF  ZINC. — Zinc  is  principal- 
uscs  of  zinc.  \y  employed  in  the  form  of  sheet  zinc,  for 
roofing  and  similar  purposes.  It  is  also  used,  like  tin, 
as  a  coating  to  protect  iron  chains  and  other  objects 
from  rust.  The  coating  is  effected  by  plunging  the 
iron  into  molten  zinc,  which  forms  an  alloy  upon  its 
surface.  The  iron  thus  coated  is  sometimes  called  gal- 
van' zed  iron,  though  without  reason,  as  is  evident  from 
the  above  process.  Solutions  of  zinc  are  sometimes 
used  to  prevent  the  decay  of  wood,  and  to  render  it 
less  combustible.  It  has  also  been  employed  with 
success,  as  a  substitute  for  copper,  in  sheathing  vessels. 


CLASS  IV. 

TIN. 

x 

614.     DESCRIPTION. — Tin  is  a  brilliant 

Describe  the  .          ..  „      ..  .  _ 

metal  Tin.        white  metal,  very  soft  and  malleable,  and 
From  what  t  easily  tarnished.     When  a  bar  of  tin 

ore  is  it  made?  * 

is  bent,  it  gives  a  peculiar  grating  sound, 
fancifully  called  the  cry  of  tin.  This  is  a  consequence 
of  the  friction  of  the  minute  crystals  of  tin  of  which 
it  is  composed.  Its  only  ore  is  an  oxide,  called  tin 


TIN.  249 

stone,  of  which  Cornwall,  England,  is  the  principal 
locality. 

How  is  tin  615.    PRODUCTION. — Tin    is   produced, 

produced  ?  \fae  jron  an(j  most  other  metals,  by  heating 
its  oxide  with  carbon.  The  materials  are  heated  in  a 
small  blast  furnace.  The  carbonic  oxide  produced  in 
the  fire,  as  before  explained,  is  the  reducing  agent.  It 
takes  the  oxygen  from  the  ore,  and  passes  off  with  it 
as  carbonic  acid,  while  the  metal  fuses,  and  runs  to  the 
bottom  of  the  furnace.  By  heating  tin  before  the 
blow-pipe,  it  is  rapidly  converted  into  white  oxide. 
How  do  adds  616.  ACTION  OF  ACIDS. — Tin  resists 
act  on  tin  ?  weak  acids  remarkably.  Dilute  muria- 
tic and  sulphuric  acids,  which  dissolve  most  of  the 
metals  before  described,  act  upon  it  but  feebly.  The 
concentrated  acids  dissolve  it  with  comparative  ease. 
Its  solution,  although  less  poisonous  than  those  of 
lead,  are  still  injurious  to  health.  Acid  food  should, 
therefore,  never  be  allowed  to  stand  for  a  long  time  in 
tin  vessels.  The  solutions  of  tin  are  colorless. 

617.  Nitric  acid  acts  upon  tin  with  en- 

Whatisthe 

action  of  ni-  ergy ;  but,  like  a  ferocious  animal  that  de- 
tnc  acid?  stroys  without  devouring  its  prey,  leaves 
it  undissolved.  It  converts  it  into  a  white 
insoluble  powder  of  oxide  of  tin,  with  the 
evolution  of  the  usual  red  fumes.  This  case 
is  an  exception  to  the  usual  action  of  nitric 
acid.  One  portion  of  the  acid  commonly 
acts  to  produce  oxide,  while  another  portion  dissolves 
the  oxide  formed.  The  experiment  for  the  solution 
11* 


250  METALS. 

of  tin  may  be  made  with  tin-foil,  in  a  tea-cup  or  test- 
tube. 

618.  Aqua-regia,)  it  will  be  remembered. 

What  is  the  ° 

action  of  aqua-  is  a  mixture  of  nitric  and  muriatic  acids. 

regia  on  tin  ?      Jn  most  caseg  they  ^  &g  before  degcribedj 

in  concert,  to  dissolve  metals  that  neither  can  dissolve 
alone.  They  act  thus,  also,  upon  tin,  in  small  por- 
tions. But  if  larger  quantities  are  employed,  the  mix- 
ture grows  warm,  and  the  nitric  acid,  as  if  stimulated 
beyond  restraint,  attacks  the  metal  for  itself,  and  con- 
verts it,  as  when  it  acts  alone,  into  a  white  powder. 

619.  COATING  PINS. — Common  brass  pins 

How  are  pins 

coated  with  are  coated,  by  boiling  with  cream  of  tartar 
tin?  and  tin-foil,  or  bits  of  tin.  The  acid  of 

the  tartar  acts  as  solvent.  Tin  is  then  deposited  on 
the  mere  electro-positive  brass,  as  in  cases  of  galvanic 
decomposition.  At  every  point  where  brass,  tin,  and 
the  liquid  are  in  contact,  a  small  galvanic  battery  is,  in 
fact,  produced. 

How  is  tin  620.     TIN  WARE. — Tin  is  cast  in  va- 

plate  made  ?  rious  forms,  for  culinary  and  chemical  uten- 
sils. A  little  lead  is  added  to  give  it  greater  tough- 
ness. Common  tin  ware  is  made  of  sheet-iron,  coated 
with  tin.  The  coating  of  the  metal  is  effected  by 
dipping  well  cleaned  sheet-iron  into  molten  tin. 

621.  CRYSTALLINE  TIN. — Tin  has  a  great 

How  may  the  " 

crystalline  tendency  to  assume  a  crystalline  form. 
*tinCbele.en?  The  stmcture  may  be  observed  on  wash- 
ing the  surface  of  ordinary  tin  plate  with 
aqua-regia,  to  remove  the  thin  coating  of  oxide.  It 
may  be  still  better  seen  if  a  tin  plate  is  heated  over  a 


ANTIMONY.  251 

lamp  till  the  coating  melts,  then  suddenly  cooled,  and 
afterward  cleaned  as  above  directed.  The  whole  sur- 
face is  then  found  to  be  covered  with  beautiful  crys- 
talline forms. 


AOTIMONY. 

Describe  the          622.   DESCRIPTION.  —  Antimony  is  a  blu- 
ish  white  and   hi§hly  crystalline    metal 


what  ore  is  it     which  does  not   tarnish  in  the  air.     It  is 

obtained?  1-11 

so  brittle  that  it  may  be  readily  reduced  to 
powder.  The  ore  from  which  the  metal  is  produced  is 
the  grey  sulphuret,  or  antimony  glance. 

623.    PRODUCTION.  —  Antimony  may  be 

How  is  anti-  .  . 

monypro-  obtained  from  its  oxide,  by  the  usual  pro- 
cess of  reduction.  The  sulphuret  is  first 
partially  converted  into  oxide  by  roasting,  and  still  fur- 
ther by  carbonate  of  soda,  which  is  added  in  the  sub- 
sequent process.  It  is  then  mixed  with  charcoal,  and 
intensely  heated  in  crucibles.  At  a  white  heat  the 
metal  fuses,  and  sinks  to  the  bottom.  The  soda  added 
in  the  process  exchanges  its  oxygen  for  the  remaining 
sulphur  of  the  ore. 

624.  ACTION  OF  HEAT  AND  AIR.  —  If  heated 

How  may  an-      ...  ,  •,«»  4 

timony  be  before  the  blow-pipe,  antimony  soon  melts, 
and  burns  with  a  white  flame.  It  is  at  the 
same  time  converted  into  oxide.  A  portion  of  the  oxide 
escapes  into  the  air,  while  the  rest  forms 
a  white  coating  upon  the  charcoal  sup- 
port. At  the  high  temperature  which 
is  here  produced,  the  affinity  of  the 


252  METALS. 

metal  for  oxygen  is  so  stimulated,  that  the  molten 
globule  will  continue  to  burn,  even  if  removed  from 
the  flame.  By  directing  a  stream  of  air  upon  it, 
from  a  pipe-stem,  the  combustion  may  be  maintained 
till  the  globule  is  entirely  consumed. 

625.  If  the  molten  globule  be  allowed 

Describe  an  P  ,,  ,,        n  ••• 

experiment        to  fall  upon  the  floor,  it    im-        . 
with  the  mol-     mediately    divides     into    hun-    x 

ten  globule?  '"^         >•      • 

dreds  of  smaller  globules,  which  —jjjs&Z... 
radiate  in  all  directions,  leaving  each  a  dis-  - '//',  I  V\\ 
tinct  track  of  white  oxide  behind  it. 
What  is  the          626.    ACTION  OF  CHLORINE. — A  shower 

rinelnanti-'  of  fire  may  be  Produced ^Y  sprinkling  fine 
many  ?  powder  of  antimony  into  a  vial  containing 

chlorine  gas.  The  metal  is  hereby  converted  into  a 
white  smoke  of  chloride  of  antimony.  In  its  rela- 
tions to  the  principal  acids,  antimony  resembles  tin. 
Its  solutions  are  colorless. 

627.  USES  OF  ANTIMONY. — The  principal 

What  are  the  f  .  . 

principal  uses  use  of  antimony  is  in  the  preparation  of 
of  antimony?  alloySj  io  ^Q  hereafter  described.  Among 

these,  type  metal  is  the  most  important.  Many  of  the 
compounds  of  antimony,  like  other  poisonous  sub- 
stances, are  used  with  advantage  in  medicine.  Tartar 
emetic  is  one  of  these  medicinal  compounds  contain- 
ing antimony. 


BISMUTH  253 

CLASS  V. 

BISMUTH. 

Bismuth— -de-        ^^'  DESCRIPTION. — Bismuth  is  a  brittle, 
script-fan,  sol-    crystalline  metal,  of  a  reddish  white  color. 

vents,  and  oc-  .  . 

currence  in  It  is  used  in  making  certain  alloys.  Like 
antimony,  it  can  be  readily  ground  to  pow- 
der. Crystals  of  bismuth  may  be  obtained  by 
the  method  described  in  the  section  on  sulphur, 
as  represented  in  the  figure.  Nitric  acid  is  its 
proper  solvent,  and  forms  with  it  a  colorless  solution. 
Bismuth  is  found  native,  forming  threads  of  metal  in 
quartz  rock.  Its  most  productive  localities  are  in 
S  axony. 

629.  PRODUCTION. — The  metal  is  pro- 

How  is  bis-  . 

muthprodu-      cured  from  the  rock  which  contains  it,  by 
simple  heating,   in  inclined    tubes.     At  a 
comparatively  moderate  temperature  the  bismuth  fuses 
and  runs  down  into  vessels  placed  to  receive  it. 

630.  EFFECT  OF  HEAT  AND   AIR. — The 

What  is  its 

action  before     same    experiments   before    the  blow-pipe, 
thcbloiv-pipc?   and  with  moiten  globules,    which    were 

described  in  the  case  of  antimony, 
may  be  made  with  bismuth.  The 
only  difference  is,  that  the  metal  does 
not  burn  with  flame,  and  that  the  coat- 
ing of  oxide  on  the  charcoal  is  yellow,  instead  of  white. 

631.  USES  OF    BISMUTH. — Its  principal 

What  are  the 

uses  of  bis-        use   is  in  the  preparation  of  alloys,  to  be 
muth?  described  hereafter.     One  of  them  has  the 


254 


METALS. 


remarkable  property  of  fusing  in  boiling  water.  Seve- 
ral compounds  of  bismuth  are  used  in  medicine  ;  the 
sub-nitrate,  is  also  employed  as  a  cosmetic.  This 
use  of  it  is  quite  hazardous,  as  certain  gases  which  are 
often  present  in  the  air.,  have  the  effect,  as  will  be  here- 
after seen,  of  changing  its  color  to  a  deep  brown  or  black. 


Copper  —  de- 
scription, 
ores,  solvents? 


COPPER. 

632.  DESCRIPTION.  —  Copper  is   a  red, 
malleable,  and  highly  tenacious  metal.     It 

tamishes   in  the  ^    but  ig  ]ess    injure(}  fty 

rust  than  iron,  and  therefore  more  durable.  Nitric  acid 
is  its  proper  solvent,  and  forms  with  it  a  green  solution. 
Copper  is  found  in  abundance,  in  the  metallic  condi- 
tion, on  the  southern  shore  of  Lake  Superior.  It  is 
chiseled  out,  in  masses,  from  the  rocks  which  contain 
it.  The  metal  is  more  commonly  obtained  from  a 
mineral,  called  copper  pyrites,  which  is  a  double  sul- 
phuret  of  iron  and  copper.  It  is  also  found  as  pure 
sulphuret,  red  oxide,  and  carbonate.  Minute  traces  of 
copper  are  found  in  human  blood. 

633.  PRODUCTION.  —  Copper  is  prepared 

State  briefly 

the  mode  of      from  the  impure 

production.          sulphuretj         by 

first  burning  out  the  sulphur, 

in  the   air  ;    and   secondly, 

heating    with    charcoal,    to 

remove    the   oxygen  which 

has  taken   its  place.     Sand 

is  at  the  same  time  added,  to  form  a  floating  slag  with 

the  oxide  of  iron,  and  thus  remove  it  from  the  molten 

copper. 


COPPER.  255 

The  oxide  of  iron  thus  removed,  is  derived  from  the 
sulphuret  of  iron,  which  is  a  usual  constituent  of  cop- 
per ores. 

634.    Both  of  the  above  processes  of 

State  further 

particulars  of    roasting  and  heating  with  charcoal,  and 
epro  sand,    must    be    several    times    repeated 

before  pure  metallic  copper  is  obtained.  It  is  to  be 
remarked  that  the  formation  of  a  slag,  which  shall 
remove  this  iron,  depends  on  the  fact  that  its  oxide  is 
by  no  means  so  easily  reduced  as  copper.  Being  once 
brought  into  the  state  of  oxide,  it  remains  in  this  con- 
dition and  unites  with  the  silicic  acid  of  the  sand. 

635.  ACTION  OF  HEAT  AND  AIR. — Copper 
What  is  the        ,  .,..,. 

effect  of  heat  is  readily  oxidized  m  the  air,  at  a  high 
temperature.  Its  oxidation  may  be  ob- 
served, by  holding  a  copper  coin  in  the  flame  of  a  spirit 
lamp,  as  described  in  the  section  on  Flame.  The  iri- 
descent hues  observed  in  the  experiment,  are  owing  to 
the  varying  depth  of  oxide  on  different  portions  of 
the  coin.  By  long  continuation  of  the  process,  the 
whole  surface  is  converted  into  black  oxide.  If  it  be 
sooner  suspended,  and  the  coin  plunged  into  cold 
water,  a  coating  of  red  oxide  containing  less  oxygen 
is  obtained. 

636.  USES  OF  COPPER. — Copper  is  used 

Mention  some  .  .   .    ,       . 

of  the  uses  of  ior  a  variety  of  purposes,  for  which  iron 
copper.  would  be  less  suitable,  on  account  of  its 

rapid  oxidation.  Its  employment  in  sheathing  ships,  is 
an  example.  It  is  also  a  constituent  of  various  alloys, 
to  be  hereafter  described.  Among  these,  all  gold  and 
silver  coins,  and  the  metal  of  gold  and  silver  plate,  are 
included. 


256 


METALS. 


LEAD. 

637.  DESCRIPTION. — Lead  is  a  bluish 
scription,  ores  grey  metal,  extremely  malleable,  and  read- 
and  solvents?  ^  tarnished  in  the  air.  It  is  heavier  than 
any  other  of  the  metals  mentioned  in  this  work,  except 
mercury,  gold,  and  platinum.  Nitric  acid  is  its  proper 
solvent,  forming  with  it,  a  colorless  solution.  The 
principal  ore  of  this  metal,  is  galena,  or  sulphuret  of 
lead.  Lead  is  also  found  as  carbonate,  sulphate,  and 
phosphate  of  lead. 

How  is  lead  638.    PRODUCTION. — Lead  is   obtained 

obtained?  from  the  sulphuret,  by  heating  it  with 
iron,  to  remove  the  sulphur.  A  mixture  of  metallic 
lead  and  sulphuret  of  iron  are 
thus  produced,  from  which 
the  lead  separates  by  its 
greater  specific  gravity.  If 
the  oxide  of  lead  could  be 
readily  obtained,  the  reduc- 
tion by  charcoal  would  be 
as  applicable  here,  as  in  the  case  of  other  metals. 

639.  A  SECOND  METHOD. — Another 
method,  is  to  heat  the  sulphuret  with  a 
portion  of  sulphate.  The  sulphate  has  a  large  supply 
of  oxygen,  while  the  sulphuret  is  destitute  of  this  ele- 
ment. The  two  may  be  mixed  in  such  proportions 
that  they  will  together  contain  just  enough  oxygen  to 
carry  off  all  the  sulphur,  as  sulphurous  acid.  This 
result  having  been  accomplished  by  heat,  the  pure 
metal  of  both  remains  behind.  As  a  preparation  for 


JSxplain  an- 
other method. 


LEAD.  257 

this  process,  a  portion  of  sulphuret  is  converted  into 
sulphate,  by  heating  in  a  reverbaratory  furnace.  Both 
parts  of  the  process  are  in  practice  united  ;  a  moderate 
heat  with  abundant  air  being  first  supplied,  a  portion 
of  sulphate  is  produced.  This  is  afterwards  more 
highly  heated,  with  the  undecomposed  sulphuret  which 
remains. 

640.    ACTION    OF   AIR    AND    HEAT. — If 

What  occurs       i-i-i  i    i     c         .1-11  •  .1 

when  lead  is  ^ea(i  is  heated  before  the  blow-pipe,  in  the 
heated  before  oxidizing  flame,  it  melts  and  disappears. 

the  blow-pipe  ? 

The  charcoal  support  becomes  at  the  same 
time  covered  with  yellow  oxide  of 
lead  or  litharge.  The  grey  coating 
which  at  first  forms  upon  the  lead,  is 
an  oxide  containing  less  oxgen.  If, 
on  the  other  hand,  litharge  is  heated  in  the  reducing 
flame,  it  is  converted  into  metal. 

641.   ACTION  OF  WATER. — Water,  with 

Wh,at  is  the  r  .  . 

action  of  water  the  help  of  the  air  which  it  always  con- 
on  lead.  tains,  acts  sensibly  upon  lead  and  becomes 
in  consequence  poisonous.  This  action  of  water  is 
most  decided  when  it  contains  no  foreign  matter.  On 
being  conducted  through  leaden  pipes  it  becomes 
therefore  more  impure  as  a  consequence  of  its  very 
purity. 

Whatprevents  642.  The  presence  of  sulphates  and  cer- 
this action?  tanl  otner  salts,  such  as  are  usually  con- 
tained in  spring  water,  prevents  this  effect.  The  very 
substances,  whose  presence  in  water  we  are  accustomed 
to  regret  as  impurities,  thus  become  our  most  efficient 
protectors  against  the  poisonous  effects  of  lead. 


258  METALS. 

643.  But  this  rule  is   not  without  ex- 

Do  impurities 

always  pro-  ception.  Certain  substances  seem  to  in- 
crease the  action.  It  is  therefore  always 
prudent  where  it  is  proposed  to  conduct  water  through 
leaden  pipes,  to  ascertain  by  direct  experiment,  whether 
the  particular  water  in  question  acts  upon  the  lead  or 
not. 

644.  ILLUSTRATION. — The  difference  in 

Describe  the  . 

experiment        the  action  of  pure  water  upon  lead,   and 
™ithlead  and    that  which  contains  foreign  substances    in 

distil  Lea  water. 

solution,  may  be  readily  proved  by  exper- 
iment. For  this  purpose,  bright  slips  of  lead  may  be 
placed  in  two  tumblers,  the  one  containing  rain  water, 
and  the  other  well  or  spring  water.  The  former  will 
soon  become  turbid  while  the  latter  remains  unaffected. 

645.  The  presence  of  lead  in  the  former 

How  may  the 

presence  of  case  may  be  still  more  strikingly  shown, 
•fawn*/  ^eUeT  ky  adding  to  the  water  a  few  drops  of  a 
solution  of  hydrosulpluric  acid.  The  for- 
mation of  a  dark  cloud  will  show  the  presence  of  lead, 
and  indicate  the  danger  to  be  apprehended. 

646.  LEAD  TREE. — Dissolve  some  crys- 

Describe  the 

lead  tree  and     tals  of  sugar  of  lead,   in  thirty  or  forty 

Us" production.     timeS    theif    bulk    °f   Wat6r>    and  fil1  a  vial 

with  the  solution.  A  strip  of  zinc,  hung 
in  the  vial,  will  branch  out  in  a  beautiful  ar- 
borescence  of  metallic  lead.  It  may  be  neces- 
sary to  clarify  the  solution  by  the  addition  of 
a  little  clear  vinegar  or  acetic  acid.  A  day  or 
two  will  be  required  for  the  completion  of 
the  experiment.  The  effect  depends  on  the 


MERCURY.  259 

superior  affinities  of  zinc  for  acetic  acid.  The  zinc 
takes  away  acid  and  oxygen  from  successive  portions 
of  the  sugar  of  lead,  and  leaves  the  particles  of  lead 
subject  to  the  laws  of  crystallization.  At  the  same 
time,  the  zinc  having  acquired  possession  of  the  acid 
and  oxygen,  comes  into  solution  as  acetate  of  zinc.  A 
similar  arborescence  is  produced  in  a  solution  of  silver 
by  metallic  mercury. 

How  are  shot  ^47.   MANUFACTURE   OF   SHOT. Shot  are 

made?  prepared  by  pouring  melted  lead  through 

perforated  iron  vessels.  The  drops  are  made  to  fall 
from  a  great  height  that  they  may  become  cooled  and 
solidified  in  their  descent.  They  are  caught  in  water 
that  their  shape  may  not  be  impaired.  Having  been 
assorted  by  means  of  seives,  they  are"  polished  in 
revolving  casks,  containing  a  small  portion  of  black  lead 
or  plumbago. 

Mention  other  ^48.     OTHER     USES      OF     LEAD.— In     the 

uses  of  lead.  form  of  sheet  lead  this  metal  is  applied 
to  a  variety  of  familiar  uses.  It  is  also  largely  em- 
ployed in  the  manufacture  of  lead  tubing.  It  is  a 
constituent  of  various  alloys,  among  which  pewter 
and  type  metal  are  the  more  important. 

CLASS  VI. 

MERCURY. 
649.  DESCRIPTION. — Mercury  is  a  white 

Mercury — de-      -    .  ,  i      /•  i  •    i      i 

scription,  sol-    fluid  metal  of  high  lustre  and  beauty.     It 

"discover™?        retains  the  fluid  condition  at  all  ordinary 

temperatures,and  is  only  rendered  solid  by 


260  METALS. 

extreme  cold.  Nitric  acid  is  its  proper  solvent.  Mer- 
cury is  sometimes  found  in  the  metallic  form,  but  more 
commonly  as  the  sulphuret  or  cinnabar,  which  is  its 
principal  ore.  It  is  said  that  the  mines  in  Mexico  were 
accidentally  discovered  by  a  native  hunting  among  the 
mountains.  Laying  hold  of  a  shrub  to  assist  him  in 
his  ascent,  he  tore  it  up  by  the  roots,  and  a  stream  of 
what  he  supposed  to  be  liquid  silver  flowed  from  the 
broken  ground. 

How  is  mer-  650.  PRODUCTION. — Mercury  is  prepared 
cury  obtained ?  from  the  sulphuret,  by  simple  roasting  in  a 
current  of  heated  air.  This  metal  yields  its  sulphur  so 
readily  to  the  oxygen  of  the  air  that  no  other  agent  is 
essential  in  its  production.  The  mercurial  vapors  pass 
along  with  the  gas,  into  tubes  or  chambers  where  the 
temperature  is  lower,  and  are  there  condensed  to  the 
liquid  form. 

Mention  other  651.  Mercury  may  also  be  produced  from 
methods.  fae  sulphuret  by  the  employment  of  iron 

filings  to  remove  the  sulphur,  as  in  the  case  of  lead. 
Burned  lime  may  also  be  used.  Its  calcium  combines 
with  the  sulphur  and  uses  its  own  oxygen  for  the 
partial  conversion  of  the  sulphuret  thus  formed  into 
sulphate  of  lime. 

652.  ACTION  OF  HEAT  AND  AIR. — Mercury, 

What  is  the  J7 

action  of  heat  like  water,  may  be  boiled  away  and  con- 
verted  into  vapor,  by  the  application  of 
heat.  At  39°  below  zero  it  freezes.  It  is 
always  to  be  borne  in  mind  in  experiments  with  this 
metal  arid  its  compounds,  that  its  fumes  as  well  as  its 
salts,  are  extremely  poisonous.  By  free  access  of  air  and 


MERCURY.  261 

moderate  heat,  mercury  may  be  gradually  converted  into 
red  oxide,  but  a  higher  temperature  expels  the  oxygen 
thus  absorbed,  and  the  oxide  is  again  converted  into 
metal.  This  production  of  a  metal  from  an  oxide,  by 
heat  alone,  is  characteristic  of  the  noble  metals.  They 
are  loth  to  obscure  their  splendor  in  rust ;  if  it  is  forced 
upon  them,  they  need  but  little  assistance  of  heat  to 
throw  it  off  and  re-assume  their  original  beauty. 

653.     AMALGAMS — GLASS     MIRRORS. — 

What  are 

amalgams?  Mercury  combines  with  many  metals  form- 
n?rs  sUvered?  *n&  comPounds  which  are  called  amalgams. 
When  the  mercury  is  in  large  proportion 
they  are  fluid.  Gold,  silver,  and  lead,  for  example, 
may  be  dissolved  in  mercury.  This  solvent  power  of 
mercury  is  usefully  applied  in  extracting  gold  from  the 
rocks  which  contain  it.  The  beautiful  silvering  of 
mirrors  consist  of  an  alloy  of  tin  and  mercury.  Tin 
foil  is  applied  to  the  glass,  and  being  afterward  drenched 
with  mercury,  the  excess  is  removed  by  pressure.  The 
tin  has  thus  absorbed  about  one-fourth  of  its  own 
weight  of  mercury. 

654.  A  copper  coin  may  be  similarly 
co°ppercoin  be  silvered,  by  rubbing  with  metallic  mer- 
curY>  or  keeping  it  well  moistened  for  some 
time  with  a  solution  of  mercury  in  nitric 
acid.  If  the  solution  is  quite  acid,  it  must  first  be 
nearly  neutralized  by  ammonia.  The  coin  is  to  be  af- 
terward polished.  The  chemical  action  which  takes 
place  in  this  case  is  similar  to  that  explained  in  the 
case  of  the  lead  tree.  By  drawing  a  line  across  a  thin 
brass  plate,  with  a  pen  dipped  in  solution  of  mercury, 


METALS. 

the  plate  will  be  so  weakened  that  it   may  afterward 
be  readily  broken. 

655.  OTHER  USES  OF  MERCURY. — The 
Mention^  some  compounds  of  mercury  are  extensively 
mercury.  used  in  medicine.  Corrosive  sublimate,  a 

poisonous  chloride  of  mercury,  is  employed 
for  the  destruction  of  vermin.  It  is  also  used  in  what 
is  called  the  kyanizing  process,  to  impregnate  wood 
and  other  vegetable  and  animal  substance,  and  thus 
prevent  their  decay.  Another  important  use  of  mer- 
cury is  found  in  the  manufacture  of  barometers  and 
thermometers.  It  is  especially  adapted  to  the  measure- 
ment of  heat,  by  its  fluidity  at  low  temperatures,  and 
its  ready  and  equable  expansion. 


SILVER. 

656.  DESCRIPTION. — Silver  is  a  lustrous 
scription,  ores    white  metal  of  perfect  ductility  and  malle- 

and  solvents?      abiljtVi       Itg  1QSS  Qf   ]ustre  QJ1    exposure,    is 

owing  to  the  presence  of  a  small  proportion  of  sulphur- 
etted hydrogen  in  the  air.  Nitric  acid  is  its  proper  sol- 
vent, though  for  certain  purposes  oil  of  vitriol  is  pre- 
ferred. Silver  is  often  found  native,  but  moro  fre- 
quently combined  with  sulphur  as  silver  glance. 
Galena  or  sulphuret  of  lead  always  contains  it  in  small 
proportion,  and  sometimes  to  the  amount  of  one  or 
two  per  cent. 

How  is  silver  && •  PRODUCTION. — Silver    is   prepared 

obtained?         from  the  sulphuret,  by  first  roasting  the  ore 


SILVER. 


263 


with  common  salt,  in  order  to  convert  it  into  chloride. 
Iron  is  subsequently  employed  to  remove  the  chlorine, 
and  isolate  the  metallic  silver. 

Give  the  com-  658.  Mercury  is  added  with  the  iron,  in 
piete  process.  orcjer  ^^  jt  may  djssoive  the  silver  from 

the  mass  of  roasted  ore  and  iron,  as  fast  as  it  is  formed' 
The  materials  are  agitated  with  water  for  many  hours 
together.  At  the  end  of  the  process  the  mercury,  with 
its  load  of  silver,  is  drawn  off  from  the  bottom  of  the 
cask.  The  solution  of  silver  in  mercury  is  afterward 
filtered  through  buckskin  or  closely  woven  cloth,  which 
allows  a  large  part  of  the  liquid  metal  to  pass,  while 
the  silver  with  a  small  portion  of  mercury  is  detained. 
The  silver  is  then  freed  of  its  remaining  mercury  by 
heat.  The  above  process  is  called  amalgamation. 

659.    SILVER    OBTAINED    FROM    LEAD.  — 

Describe  the 

process  for        Almost  all  lead,   as  produced  from  galena 


and  its  other  ores'  contains  a  certain  pro- 
portion of  silver.  The  latter  metal  may 
be  freed  from  a  large  part  of  the  lead  by  melting  the 
alloy  and  then  allowing  it  to  cool  slowly.  Most  of 
the  lead  solidifies  in  small  crystals,  and  may  be  skim- 
med out  with  an  iron  cullender.  An  alloy  containing 
silver  in  large  proportion  remains  in  the  liquid  condi- 
tion. It  is  afterwards  solidified  by  further  cooling. 
The  above  is  called  Pattinson's  process. 

660.   CUPELLATION.  —  The  remainder  of 
How  is  the  re-    jeac[   js  separated  from  the  silver  by  con- 

maimng  lead 

separated?        verting  it  into  oxide,  in  a  current  of  heated 

air.      The  silver   does  not   oxidize   under 

these   circumstances,   but   retains   the   metallic   form. 


264  METALS. 

The  mass  of  metal  grows  smaller  as  the  process  pro- 
ceeds, till  finally  pure  silver  remains.  The  moment 
of  its  production  is  indicated  by  a  beautiful  play  of 
colors  and  a  sudden  brightening  of  the  metal.  The 
above  process  is  carried  on  upon  a  hollowed  and  com- 
pacted mass  of  bone-ash,  called  a  cupel.  The  object  of 
the  cupel  is  not  alone  to  support  the  metal,  but  to  ab- 
sorb the  hot  and  fused  oxide  of  lead  as  fast  as  it  is 
formed.  If  a.  little  copper  is  present,  it  is  also  absorbed 
with  the  lead.  The  process  is  called  cupellation. 

661.  It   may  be   illustrated  on  a  small 

How  mcf/  the 

process  be  u~      scale,  by  making  an  excavation  in  a  piece 
lustrated?         Qf  c[iarcoa])  an(j  pressing  into  it  a  lining 

of  well  burned  and  moistened  bone 
ash.  A  globule  of  lead,  to  which  a  little 
silver  has  been  added,  is  to  be  heated, 
on  the  support,  in  the  oxidizing  flame. 
For  separating  a  small  quantity  of  lead  from  silver, 
the  bone  ash  is  not  essential.  The  process  may  be 
conducted  before  the  blowpipe,  upon  the  naked  char- 
coal. A  small  portion  of  silver  may  often  be  obtained 
from  the  lead  of  commerce  by  this  means. 
What  is  said  662.  SILVER  COIN. — The  standard  sil- 
of  silver  coins?  ver  of  the  United  States  is  an  alloy  con- 
taining ten  per  cent,  of  copper.  Silver  plate  should 
have  the  same  composition.  The  object  of  alloying 
with  copper,  is  to  impart  greater  hardness  to  the  metal, 
and  secure  against  the  gradual  loss  from  attrition,  which 
would  otherwise  occur.  Spanish  silver  often  contains 
a  small  proportion  of  gold.  The  gold  is  left  as  a  black 


SILVER.  265 

powder,  in  dissolving  such  coins  in  nitric  acid.     Its 
color  and  lustre  may  be  brought  out  by  rubbing. 

663.  THE  SILVER  ASSAY. — Assaying  is 

What  is  as-  ,  n  ,, .         » 

laying,  and  tne  process  by  which  the  proportion  of  met- 
why  necessa-  ais  jn  an  a}}oy  js  ascertained.  In  all  estab- 
lishments where  money  is  coined,  assaying 
is  an  important  part  of  the  work  of  the  establishment. 
The  precious  metals,  as  received  at  the  mint,  commonly 
contain  a  certain  proportion  of  other  metals.  But  it 
may  be  too  much  or  too  little.  It  is  the  business  of  the 
assayer  to  ascertain  its  precise  composition,  that  the 
metal  may  be  rendered  purer,  if  necessary,  or  be  fur- 
ther alloyed,  if  found  purer  than  the  standard. 

664.  As  a  preparation  for  the  silver  as- 

Descmbc  the 

process  of  as-  say,  a  sample,  containing  an  ounce,  or  other 
definite  weight  of  the  impure  metal,  is  dis- 
solved in  nitric  acid.  The  dissolved  silver  has  the  pro- 
perty of  becoming  solid  again,  and  sinking 
to  the  bottom  of  the  clear  solution  as  a  white 
curd,  just  in  proportion  as  common  salt  is  fur- 
nished to  it.  But  the  other  metals  which 
may  be  present,  as  impurities,  have  no  such 
effect.  It  follows,  that  the  amount  of  silver 
present,  is  just  in  proportion  to  the  amount  of 
salt  it  is  necessary  to  supply,  before  the  pre- 
cipitation, or  formation  of  the  curd,  ceases.  Now,  the 
assayer  knows  beforehand,  how  much  salt  he  must 
supply  to  the  solution  of  an  ounce  of  metal,  if  it  be  all 
silver.  If  he  finds  that  an  ounce  of  the  sample,  re- 
quires to  be  supplied  with  the  same  quantity,  before  the 
precipitation  ceases,  he  knows  that  the  metal  is  all  silver  ; 

12 


266  METALS. 

if  but  half  as  much  is  required,  he  knows  that  it  is 
but  half  silver.  Having  ascertained  the  true  proportion, 
the  assay  is  completed.  The  salt  required  in  the  pro- 
cess is  employed  in  the  form  of  a  solution,  and  the 
quantity  used  is  known  by  pouring  it  from  a  graduated 
vessel. 

665.  EXPLANATION. — The  curd,  which 

Explain  the 

chemical  ac-  forms  in  the  above  process,  is  insoluble 
abovTprocess.  chloride  of  silver,  formed  from  the  silver  of 
*  the  solution,  and  the  chlorine  of  the  salt. 
The  nitric  acid  and  oxygen,  which  were  combined 
with  the  silver,  at  the  same  time  unite  with  the  sodium, 
forming  nitrate  of  soda,  which  remains  in  solution. 

666.  SILVER  SEPARATED  FROM  COPPER. 
Describe  the  ,•••/. 

method  of  ex-  Copper,  obtained  from  certain  ores,  con- 
tams  so  mucn  silver  as  to  make  their  separa- 
tion an  object  of  importance.  The  method 
pursued  is,  to  fuse  the  copper  with  lead.  As  the  lead 
flows  out  again  by  subsequent  fusion,  it  brings  with  it 
all  the  silver,  and  the  copper  remains  behind  as  a  spongy 
mass.  This  process  is  called  liquation.  The  silver  is 
then  freed  from  lead  by  the  process  of  cupellation  al- 
ready described. 

Mention  some  ^67.      IfsES     OF     SILVER. Most    US6S    of 

uses  of  silver,  silver  are  so  familiar  that  they  need  not  be 
here  mentioned.  Its  employment  for  daguerreotype 
plates  depends  on  the  fact  that  the  color  of  many  of 
its  compounds  is  readily  changed  by  light.  This  sub- 
ject is  more  fully  considered  in  the  section  on  chlo- 
rides. The  nitrate  of  silver,  or  lunar  caustic,  is  used 
in  surgical  operations,  to  burn  or  cauterize  the  flesh. 


GOLD.  267 

In  solution,  it  is  also  employed  as  a  hair  dye,  and  in 
the  production  of  indelible  ink. 


GOLD. 


Mention  some  668.  DESCRIPTION.  —  Gold  is  a  yellow 

properties  of  metai  of   brilliant  and  permanent  lustre. 

gold?    Its  sol-  ± 

vent?    and  Its  extreme  malleability  is  strikingly  illus- 

occurrence? 


into  a  leaf  but  little  more  than  ¥^J¥¥¥  of  an  inch  in 
thickness.  As  the  fact  may  be  otherwise  stated,  a  cube 
of  gold,  five  inches  on  a  side,  could  be  so  extended  as 
to  cover  more  than  an  acre  of  ground.  Such  gold  leaf 
is  permeable  to  hydrogen.  A  jet  of  this  gas  may  be 
blown  through  it  and  kindled  on  the  opposite  side. 
Gold  is  proof  against  all  ordinary  acids,  excepting  aqua- 
regia.  It  is  found  only  in  the  metallic  state,  and  com- 
monly either  in  quartz  rock  or  in  the  sands  of  rivers. 
Native  gold  contains  from  five  to  fifteen  per  cent,  of 
silver. 

How  is  pure  ^69.    PRODUCTION.  -  THE  REFINING  PRO- 

goid  produced?  CESS.  —  Native  gold  may  be  freed  from  the 
silver  which  it  contains,  by  the  agency  of  concentrated 
sulphuric,  or  nitric  acid.  A  difficulty  in  accomplishing 
this  result  arises  from  the  fact  that  every  particle  of  silver 
is  so  perfectly  surrounded  by  gold,  that  the  acid  does 
not  readily  reach  it.  This  difficulty  is  overcome  by 
fusing  more  silver  into  the  gold,  and  thus  opening  a 
passage  for  the  solvent.  This  being  done,  both  the 
original  silver  and  that  which  has  been  added,  are  read- 
ily removed.  The  above  is  the  process  at  present  pur- 
sued in  France  for  refining  gold. 


268  METALS. 

Describe  an-  670.    ANOTHER     METHOD. The    SGCOIld 

other  method.  method  is  essentially  the  same  as  that  al- 
ready described,  with  the  substitution  of  nitric  for  sul- 
phuric acid.  The  addition  of  silver,  as  a  preliminary 
step,  is  found  necessary  in  this  process  also.  So  much 
silver  is  added,  that  the  gold  forms  but  a  quarter  of  the 
mass  exposed  to  the  action  of  the  acid.  The  method 
is  hence  called  quartation.  *  The  process  involves  a 
previous  knowledge  of  the  approximate  composition 
of  the  mixed  metal.  This  may  be  obtained  by  the 
touchstone,  as  hereafter  described. 
Whatisamal-  671.  AMALGAMATION. — Gold  may  be  ob- 
gamation?  tained  from  any  material  which  contains 
it,  even  in  small  proportion,  by  the  process  of  amalga- 
mation. This  process  consists  in  agitating  the  finely 
divided  material  with  mercury,  until  the  latter  has  ex- 
tracted all  of  the  precious  metal.  It  is  then  obtained 
from  its  solution  in  mercury,  by  the  same  means  em- 
ployed in  the  case  of  silver.  This  method  is  employed 
in  the  case  of  the  gold-bearing  quartz  of  California. 
The  dust  of  jewelers  shops  is  similarly  treated,  in  order 
to  save  the  small  proportions  of  gold  which  it  contains. 
672.  GOLD  FROM  LEAD  AND  COPPER. — 

How  is  gold  . 

separated  Certain  ores  of  lead  and  copper  contain  so 
much  §old  that  it;  is  Profitable  to  extract  it 
from  the  metal  which  they  yield.  This 
is  done  by  the  processes  of  liquation  and  cupellation  be- 
fore described. 

*  In  the  practice  of  the  United  States  Mint,  the  addition  of  less 
silver  has  been  found  sufficient.  The  proportion  of  gold  is  there 
reduced  to  one-third.  Nitric  acid  is  then  employed  in  the  refining 
process. 


GOLD.  269 

673.  GOLD  FROM  STJLPHURETS  OF  IRON, 

How  is  qold  ci    i    i  f     •  e 

obtained  from  &c.— Sulphurets  of  iron,  copper,  dec., 
certain  ml-  sometimes  contain  gold,  in  small  quantity, 
and  so  completely  disseminated  that  it  can- 
not be  readily  extracted  by  mercury.  It  has  been  found 
advantageous  to  heat  such  ores  with  nitrate  of  soda, 
previous  to  amalgamation.  The  sulphurets  are  thus 
partially  converted  into  sulphates,  which  can  be  washed 
out.  What  remains  of  the  pulverized  material  is  at 
the  same  time  thoroughly  opened  to  the  action  of  mer- 
cury. 

Describe  the          674.  THE  GOLD  ASSAY. — Gold  to  be  as- 
method of 'as-    saye(j  contains  commonly,  only  silver  and 

saying  gold  ?  .  .   .  '  '          / 

Why  is  siher  copper,  as  impurities.  By  msing  the  sam- 
ple with  lead,  and  then  removing  this 
metal  by  cupel! ation,  it  carries  with  it  the  copper,  into 
the  cupel.  A  globule,  containing  only  gold  and  silver, 
remains.  The  silver  is  then  dissolved  out  by  nitric 
acid.  The  remaining  sponge  of  pure  gold  being 
weighed,  and  its  weight  compared  with  that  of  the  orig- 
inal sample,  the  assay  is  completed.  More  silver  is 
added  in  the  process,  for  reasons  stated  in  a.  previous 
paragraph. 

What  is  the  675.    ASSAY     OF     GOLD     BY     THE     TOUCH- 

touckstone?       STONE. — Any  hard  and   somewhat  gritty 

and  how  ts  it  J  J 

used  in  assay-  stone,  of  a  dark  color,  which  is  not  acted 
on  by  acids  answers  the  purpose  of  a  touch- 
stone. The  assay  consists  in  marking  upon  the  stone 
with  the  alloy,  and  judging  of  the  purity  of  the  metal 
from  the  color  of  the  mark,  and  the  degree  in  which 
it  is  affected  by  an  acid.  Nitric  acid,  to  which  a  very 


270  METALS. 

small  quantity  of  muriatic  acid  has  been  added,  is  em- 
ployed in  this  test.  Gold  alone  is  proof  against  its 
action.  In  proportion  to  the  permanence  of  the  mark, 
is  the  purity  of  the  gold  which  has  been  submitted  to 
the  assay. 

What  is  said  676.  GOLD  COIN. — The  gold  employed 
of  gold  coin  ?  for  CQ^  plate  and  je  weiry  js  a]  ways  alloyed 

with  a  certain  portion  of  copper  or  silver,  to  give  it 
greater  hardness.  The  standard  gold  of  the  United 
States  is  nine-tenths  pure  gold,  the  remaining  tenth 
being  an  alloy  of  copper  and  silver. 

677.  PURITY  OF  GOLD. — The  purity  of 

How  is  the  de-  . 

gree  of  purity  gold  is  expressed  in  carats •,  a  carat  signify- 
mwMdr  ing'  Practicall7>  one  twenty-fourth.  Thus, 
when  gold  is  said  to  be  sixteen  carats  fine, 
it  is  meant,  that  two-thirds  of  it  is  pure  gold.  Gold 
eighteen  carats  fine  is  three-fourths  pure  gold,  and  one- 
fourth  alloy. 

678.  GILDING. — Gilding  by  the  galvanic 

How  is  copper 

jewelry  gild-  battery  has  been  already  described.  This 
method  is,  in  most  cases,  preferable  to  all 
others.  Copper  jewelry  is  thinly  gilded  by  boiling  in 
a  solution  of  gold  in  carbonate  of  soda  or  potash.  The 
solution  is  prepared  by  first  dissolving  the  gold  in  aqua 
regia,  and  afterward  precipitating  and  re-dissolving  it, 
by  means  of  the  carbonate  above  named. 

679.  Gildine  may  also  be  effected  by  an 

Describe  the  °          J 

method  of  gild-    amalgam  of  gold  and  mercury.     The  amal- 
omof  am/         £am  ^em§  applied,  the  mercury  is  expelled 
by  heat  and  the  gold  remains.     This  me- 
thod is  very  frequently  employed.     A  coating  of  pure 


PLATINUM.  271 

gold  is  produced  upon  articles  of  jewelry,  made  of  im- 
pure metal,  by  first  heating  them,  and  then  dissolving 
out  the  copper  by  means  of  nitric  acid. 

PLATLNTJM. 
680.     DESCRIPTION. — Platinum    is  the 

Platinum — 

Description,      last  of   the  noble   metals.     It    resembles 

^sofoentsT'  Stee^  m  c°l°r>  anc^  possesses  a  high  degree 
of  malleability.  It  is  the  heaviest  and  the 
most  infusible  of  all  metals.  At  a  white  heat  it  may 
be  welded,  like  iron.  Like  gold,  it  resists  the  action 
of  any  single  acid,  but  may  be  dissolved  in  aqua-regia. 
It  is  commonly  found,  like  gold,  in  small  flattened 
grains,  in  the  sand  of  certain  rivers.  Its  pecuniary 
value  is  about  half  that  of  the  more  precious  metal. 

681.  PLATINUM  CONDENSES  GASES. — The 

Mention  a  re- 
markable ef-      metal  platinum  has   the   remarkable  pro- 

PeriY  of  condensing  gases  upon  its  surface, 
and  thereby  increasing  their  affinities. 
This  effect  is  in  proportion  to  the  surface 
exposed.  It  may  be  prepared  for  this  experi- 
ment by  burning  paper,  previously  moistened 
with  a  solution  of  this  metal.  Such  an  ash, 
by  simple  exposure  to  the  air,  condenses  and 
retains  a  large  quantity  of  oxygen  within  its 
pores.  On  holding  it  in  a  jet  of  hydrogen, 
the  condensed  oxygen  immediately  unites  with  the 
latter  gas  so  energetically  as  to  inflame  it. 

682.  Platinum  is  employed  for  similar 

Give  another 

illustration  of  purposes,  in  the  form  of  a  sponge,  and  as  a 
this  effect.  powder,  called p latinum  black.  A  mixture 


272  METALS. 

of  nitric  oxide  and  hydrogen,  passed  through  a  tube  con- 
taining heated  platinum  black,  issues  from  the  tube  as 
ammonia  and  water.  The  hydrogen  has  entered  into 
combination  with  both  of  the  elements  of  the  nitric 
oxide,  producing  two  new  compounds. 
Why  isplati-  683.  OTHER  USES  OF  PLATINUM. — The 
num.  superior  m0st  important  use  to  which  platinum  is 

to  ot her  metals  _         . 

for  chemical  applied  in  the  arts,  is  in  the  manufacture 
apparatus?  o^  ^Q^^I  apparatus.  Its  extreme  in- 
fusibility  and  resistance  to  acids,  adapt  it  especially  to 
this  purpose.  In  the  manufacture  of  oil  of  vitriol,  for 
example,  no  other  material  excepting  gold  could  well 
take  the  place  of  the  platinum  vessels,  in  which  con- 
centration is  effected.  Platinum  crucibles  are  also  in- 
valuable, as  they  may  be  exposed  to  the  fire  of  a  blast 
furnace  without  injury.  Nothing  less  than  the  most 
intense  heat  of  the  oxyhydrogen  blow-pipe,  or  galvanic 
battery,  is  sufficient  to  fuse  this  metal. 


ALLOYS. 

.  684.    The  compounds  of  metals  with 

alloy?     Give    metals  are   called  alloys.     The  following 

fiontfPb°rasS     are  among  the  more  important. 
and  other  al-          Brass  is  copper,   lightened  in  color  by 
the   addition   of  one-fourth  its  weight  of 
zinc. 

German  silver  is  a  kind  of  brass,  still  further  whitened 
by  nickel.  Its  exact  composition  has  been  given  in 
another  place.  An  alloy  of  30  parts  silver,  25  of  nickel, 
and  55  of  copper  forms  a  nearly  perfect  substitute  for 
silver  for  all  ornamental  purposes. 


ALLOYS.  273 

Bronze  is  copper,  containing  ten  per  cent,  of  tin. 
Bell  metal  is  a  kind  of  bronze,  containing  tin  in  larger 
proportion. 

Pewter  is  an  alloy  of  tin  with  variable  proportions 
of  antimony  or  lead.  Britannia  ware,  so  called,  is  a 
sort  of  pewter. 

Type  metal  is  an  alloy  of  lead,  containing  twenty- 
five  per  cent,  of  copper.  By  the  use  of  tin,  instead  of 
lead,  a  better,  but  more  expensive  type  metal  may  be 
produced.  Zinc,  with  a  few  per  cent,  of  copper,  lead, 
and  tin,  has  also  been  recently  employed. 

Fine  and  coarse  solders  are  alloys  of  tin  and  lead 
the  former  being  two-thirds,  and  the  latter  one-fourth, 
tin.     Hard  solder  is  a  variety  of  brass. 

Newton's  fusible  metal,  which  has  the  remarkable 
property  of  melting  in  boiling  water,  is  composed  of 
8  parts  of  bismuth,  5  of  lead,  and  3  of  tin. 

Many  of  the  above  alloys  are  slightly  varied  in 
their  character  by  the  addition  of  other  metals  in  small 
quantity. 


274 


SALTS. 


CHAPTER  III. 

SALTS. 

SOLUTION  AND  CRYSTALLIZATION. 
„„  ,  685.    DEFINITION. — Under    the  general 

What  com- 
pounds are       head  of  salts,  are  included  all  compounds 

of  acids  and  bases,  and  beside  these,  the 
compounds  of  chlorine,  bromine,  iodine,  sulphur,  &c. 
with  the  metals.  Sulphate  of  soda,  or  blue  vitriol,  is 
an  example  of  the  first  class,  and  chloride  of  sodium, 
a  common  salt,  of  the  latter. 

686.   PREPARATION  or  SALTS. — The  salts 

Mention  some 

methodsofpre-    of  most  acids  may  be  produced,   by   sim- 

paring  salts  ?     ^  brmgmg  tne  acid    and    oxide    together. 

Sulphate  of  potassa  is  thus  produced,  from  sulphuric 
acid  and  potassa.  Heat  is  sometimes  required,  to  bring 
about  the  combination.  They  may  also  be  prepared 
from  the  carbonates.  Thus  acetate  of  lime,  is  pro- 
duced by  pouring  strong  vinegar  on  chalk,  or  carbo- 
nate of  lime.  Carbonic  acid  is,  in  such  cases,  expelled 
by  the  stronger  acid  which  is  employed.  Other  meth- 
ods of  preparing  individual  salts,  will  be  hereafter 
given. 

Explain  solu-  687.  SOLUTION. — The  particles  of  all 
tion.  bodies  are  held  together,  as  before  ex- 

plained, by  the  attraction  of  cohesion.     But  water  has 


SOLUTION.  275 

also  an  attraction  for  these  particles.  In  the  case  of 
many  substances,  it  overcomes  the  force  of  cohesion 
and  distributes  them  throughout  its  own  volume. 
Such  a  distribution,  in  which  the  solid  form  of  the 
solid  is  entirely  lost,  is  called  solution.  Different 
liquids  are  employed,  as  solvents  for  different  sub- 
stances. A  solution  is  said  to  be  saturated  when  no 
more  of  the  solid  will  dissolve  in  it. 

688.  PRECIPITATION. — In  solution,  the 

Have  the  par- 
ticles lost  their    particles   of    bodies    have    not    lost    their 

TractionThoio  property  of  cohesive  attraction.  It  is  only 
may  they  be  overcome  by  a  superior  force.  As  soon  as 

precipitated  ? 

this  is  weakened,  they  unite  again  to  form 
a  solid.  The  solvent  power  of  alcohol  for  camphor,  is 
thus  diminished  when  water  is  added  to  the  solution. 
As  a  consequence,  the  camphor  immediately  re- 
assumes  the  solid  form.  When  a  solid  is  thus 
re-produced  as  a  liquid,  it  is  called  a  precipit- 
ate. The  above  experiment  is  made,  by  ad- 
ding water  to  an  ordinary  solution  of  camphor. 

689.  One  case  of  precipitation  is  men- 

Mention  two          .          i   •        i  T 

general  mcth-  tioned  m  the  preceding  paragraph.  But  it 
ods  of  precip-  mav  ^e  effected  by  various  methods.  All 

ttation  f  * 

of  these  may  be  arranged  under  two  heads  ; 
precipitation  by  changing  the  character  or  quantity  of 
the  solvent,  and  precipitation  by  changing  the  sub- 
stance dissolved. 

Mention  three  690.    CHANGE    OF    SOLVENT. The    three 

'b'      cases  in  which  precipitation  is  effected  by 
ye  of  sol-    changes  in  the  solvent,  are,  mixing,  cooling, 
and  evaporation.     The  first  has  just  been 


276  SALTS. 

described.  The  second  is  illustrated  in  the  production 
of  alum  crystals,  by  cooling  a  hot  solution.  The  third 
consists  in  dissolving  a  solid  in  some  liquid,  and  then 
boiling  away  the  latter.  The  experiment  may  be  tried 
with  a  saturated  solution  of  salt  and  water.  As  fast  as 
the  water  is  boiled  away,  the  portion  which  has  lost  its 
solvent,  re-assumes  the  solid  form. 

691.  CHANGE  OF  SUBSTANCE  DISSOLVED. 

Describe  two  , .        ,        ,     . 

cases  by  The  change  in  the  substance  dissolved,  is 

Stance' °^ mb'  effected?  in  some  cases>  by  addition,  and  in 
others  by  subtraction.  Carbonic  acid, 
blown  through  lime  water,  precipitates  it,  by  addition. 
The  precipitate  is  chalk,  or  carbonate  of  lime.  Pot- 
ash, added  to  a  solution  of  sulphate  of  copper,  precip- 
itates it  by  subtraction  ;  the  precipitate  is  oxide  of 
copper,  deprived  of  its  acid  by  the  potash. 

692.  EXPLANATION. — The  above   cases 

State  the  cause       f  .    .  ,  ~ 

of  predpita-  of  precipitation,  demand  some  further  ex- 
hon.  m  the  planation.  As  fast  as  carbonic  acid  is  blown 

above  cases. 

into  the  lime  water,  in  the  first  case,  the 
new  substance,  chalk,  or  carbonate  of  lime,  is  produced 
throughout  the  liquid.  We  may  suppose  that  innume- 
rable particles  are  first  formed,  before  they  unite  to 
form  a  precipitate.  But  the  cohesive  attraction  put 
forth  by  the  particles  of  this  new  compound  is  so  great 
that  the  opposing  attraction  of  the  water  is  overcome, 
they  rush  together,  and  assume  the  solid  form  of  a  pre- 
cipitate. This  did  not  happen  in  the  case  of  lime  alone, 
because  the  cohesive  attraction  between  its  particles  is 
inferior  to  the  opposing  attraction  of  the  water.  The 
second  case  is  to  be  similarly  explained. 


COHESION.  277 

693.  RELATION  OF  COHESION  AND  AFFIN- 

What  is  said 

of  the  relation  iTY. — The  chemical  affinity  of  potassa  for 
"/ndaffinit  ?  carbonic  acicl,  is  evidently  greater  than  that 
of  lime.  The  former  base  retains  the  acid 
so  firmly,  that  no  degree  of  heat  can  effect  it,  while 
the  latter  gives  up  its  acid  with  readiness,  under  the 
influence  of  a  high  temperature.  Notwithstanding  the 
superior  affinity  of  potassa,  lime  will  take  from  it,  its 
carbonic  acid,  if  added  to  a  solution  of  carbonate  of 
potassa,  in  water.  The  mixture  being  made,  the  par- 
ticles in  this  and  in  all  similar  cases,  tend  to  re-arrange 
themselves  in  the  solid  form.  They  seem  to  do  this 
without  reference  to  their  chemical  affinities,  in  such  a 
manner  as  best  to  resist  the  solvent  action  of  the  water, 
or  other  liquid.  Carbonate  of  lime  resists  such  action 
better  than  carbonate  of  potassa.  The  former  is  there- 
fore produced.  The  cohesion  of  carbonate  of  lime, 
using  the  term,  in  the  sense  of  capacity  to  resist  the 
separating  power  of  water,  has  therefore  determined 
the  production  of  this  substance,  in  opposition  to  or- 
dinary chemical  affinities, 

694.  The  above  case  illustrates  a  gene- 

Statc  and  il- 
lustrate the  ral  law.  Two  substances,  which  when 
general  law?  Qnite(j  form  an  insoluble  compound,  gen- 
erally unite  and  produce  it,  when  they  meet  in  so- 
lution. To  illustrate  by  another  example :  phos- 
phate of  lime,  or  bone  ash,  is  insoluble.  Then 
we  may  be  sure  that  phosphoric  acid  and  lime,  if 
brought  together  by  mixing  two  solutions,  will  de- 
sert any  substances  with  which  they  were  before 
combined,  and  unite  to  form  insoluble  phosphate  of 

12* 


278  SALTS. 

lime.  This  rule  is  not  without  exceptions,  but  it 
enables  the  chemist  to  determine  beforehand  innume- 
rable cases  of  precipitation. 

695.  SOLUTION  AND  CHEMICAL  COMBINA- 
tion  differ  TioN. — Solution  differs  from  chemical  com- 
bination  in  tne  varying  proportions  in 
which  it  occurs  according  to  tempera- 
ture, and  in  the  absence  of  any  change  of  chemical 
properties.  Nitre,  for  example,  dissolves  in  water,  at 
100°,  in  nearly  double  the  quantity  which  will  dis- 
solve at  70°.  At  the  same  time,  it  forms  a  solution  to 
which  it  has  imparted  its  own  chemical  properties 
unchanged. 

596.    Another  important  distinction  is 

State  another  , 

important  found  in  the  following  fact.  While  chem- 
twn'  ical  combination  is  most  active  between 
bodies  whose  properties  are  most  opposed,  such  as  fat 
and  resins,  solution  occurs  most  readily  in  the  case 
of  similar  substances.  The  metals  dissolve  in  mer- 
cury. Salts  dissolve  in  water.  Fats  and  resins  dissolve 
in  alcohol  and  ether,  which,  like  themselves,  contain 
much  hydrogen. 

697.  CRYSTALLIZATION. — In  passing  from 

What  is  said  ,r 

o/  crystalline    the  liquid  to  the  solid  condition,  the  par- 

arrangement?     ^^   Qf  mogt  bodieg  assume  a   crystalline 

arrangement.  Their  mutual  attraction  is  more  than 
a  mere  force  which  draws  and  binds  them  together. 
It  groups  them  in  regular  forms.  The  crystals  thus 
produced  are  often  too  small  to  be  separately  seen.  But 
even  where  this  is  the  case,  the  crystalline  structure  is 
readily  observed.  Surfaces  of  zinc,  or  cast  iron,  ex- 


CRYSTALS. 


279 


How  may 

' 


posed  by  recent  fracture,  are  familiar  examples.  But 
where  the  circumstances  are  favorable  for  the  forma- 
tion of  individual  and  separate  crystals,  the  most  beau- 
tiful and  symmetrical  forms  are  often  the  result. 

698.  PRODUCTION  OF   CRYSTALS.  —  Most 

. 

of  the  salts  to  be  described  in  this  cnap- 
produced?        ter  may  be  0^^  jn  tne  form  of  crys- 

tals, by  evaporating  or  cooling  their  saturated 
solutions.  The  method  by  cooling,  has  already 
been  described,  in  the  Chapter  on  Water.  In 
obtaining  crystals  by  evaporation,  the  solution 
is  to  be  moderately  heated,  in  a  saucer  or  other 
vessel.  The  crystals  formed  by  either  method, 
commonly  contain  water,  which  becomes  part  of 
the  solid  crystal,  and  is  called  water  of  crystalliza- 
tion. 

699.  VARIETY  OF  CRYSTALS.  —  The  forms 
of  leaves  and  flowers  are  scarcely  more  va- 
rious than  those  of  crystals.    The  latter  are, 
as  it  were,  the  flowers  of  the  mineral  world, 

as  distinctly  characterized  in  their  peculiar  beauty  as 
the  flowers  that  bloom  in  the  air  above  them.  Even 
where  color  fails,  the  eye  of  science  distinguishes  pe- 
culiar features  which  often  enable  it  to  determine  the 
nature  of  a  substance,  from  the  external  crystalline  form 

which  it  assumes. 

1234  5 


How  may  the 
variety  of 
crystals  be  il- 
lustrated ? 


280  SALTS. 

What  is  said  700'  FoRMS  OF  CRYSTALS.—AS  every 
of  the  variety  flower  has  its  own  distinctive  form  of 

of  forms  in  a      .  ,  . 

single  sub-  leaves  and  petals,  so  every  substance  has 
its  own  form  or  set  of  forms  from  which  it 
never  essentially  varies.  Among  these,  or  its  combi- 
nations, it  is,  as  it  were,  left  free  to  choose  in  every 
crystal  which  it  builds.  The  mineral  quartz,  which 
caps  its  prismatic  palace  with  a  hexagonal  pyramid,  is 
an  example.  Its  common  form  represented  in  Fig.  4, 
is  a  combination  of  the  prism  and  double  six-sided  py- 
ramid, which  commence  the  series. 

701.  A  form  similar  to  the  double  six- 

D escribe  some 

forms  of  a  sided  pyramid,  with  faces  corresponding  to 
single  set.  -^  twejve  converging  edges,  belongs  to  the 
same  set.  Double  pyramids  similar  to  each  of  these,  but 
of  one-half  or  one-third  their  relative  height,  or  differing 
from  them  by  some  other  simple  ratio,  also  belong  to 
the  same  set  of  forms.  Fig.  3  represents  a  form  com- 
posed of  two  of  these  pyramids.  Fig.  5  represents 
another  form  in  which  one  of  them  is  modified  by  two 
faces  of  a  prism.  To  all  of  these  and  certain  other  in- 
timately related  forms,  the  imaginary  privilege  of  se- 
lection and  combination,  above  referred  to,  extends. 
But  most  substances,  like  quartz,  as  above  described, 
affect  some  particular  shape  or  combination  in  which 
they  usually  appear. 

702.  MODIFICATIONS    OF    CRYSTALS. — 

What  modifi-      _  ... 

cations  of  the     Whatever  the  form  or  combination  may  be, 

may  occur?       ^  *s  su806?^6  of  variation,  in  any  degree, 

so  long  as  its  angles  correspond  to  those  of 

the  perfect  shape.     Thus  the  mineral  quartz,  in  its 


CRYSTALS.  281 

commonly  occurring  combination,  is  not  restricted  to  a 
perfectly  symmetrical  shape,  like  that  above  presented. 
It  may  develop  one  surface  and  diminish  the  others  to 
any  extent.  Forms  such  as 
are  represented  in  the  margin 
result.  Different  as  they  seem, 
it  will  be  observed  that  they 
agree  precisely  with  the  per- 
fect shape  in  the  angles  be- 
tween the  surfaces  of  the  prism  and  pyramid,  and  the 
different  surfaces  of  each.  In  this  their  identity 
as  crystalline  forms  consists.  It  would  thus  seem  that 
nature  pays  exclusive  attention  to  the  corners  and  an- 
gles in  her  various  systems  of  crystalline  architecture. 
703.  The  least  variation  of  the  relative 

What  consti-  .....  , 

tutes  a  new  length  of  the  vertical  axis  that  is  not  by 
some  simple  ratio,  constitutes  a  new  and 
distinct  form.  This  has  its  related  forms  as  before, 
the  whole  making  a  new  and  distinct  set,  to  which  the 
choice  of  any  substance  that  enters  it,  is  limited. 

704.    SYSTEMS    OF    CRYSTAL   FORMS. — It 

Define  ano- 
ther system  of   will  be  obvious  to  the  student  that  the  sub- 

CformsliUe  stitution  of  an  octahedron,  such  as  is  re- 
presented in  the  accompanying  figure,  for 
the  double  six-sided  pyramid,  would  be  the 
starting  point,  of  an  entirely  distinct  system  of 
forms.  Within  its  limits  there  might  be  in- 
numerable sets  as  before.  It  would  be,  as  it 
were,  the  type  of  a  new  order  of  crystalline  architec- 
ture, susceptible  of  variations  consistent  with  the  ge- 
neral style. 


282 


SALTS. 


Define  the  705.  A  third  system  is  characterized  by 

fourth^  inequality  in  three  principal  dimensions. 
systems.  The  axis  or  lines  connecting  the  solid  an- 

gles in  the  octahedron,  and  joining  the  faces  in  the 
prism,  are  all  unequal.  As  each  axes  may  be  indefi- 
nitely varied  in  this  system,  there  is  room  wthin  its 
limits  for  still  greater  variety  than  before.  The  fourth 
system  differs  from  the  third  in  an  oblique  position  of 
some  one  of  the  unequal  axes.  The  student  will 
readily  imagine  certain  oblique  forms  which  it  in- 
cludes. The  fifth  system  is  characterized  by  an  ob- 
lique position  of  three  unequal  axes.* 


706.  The  regular  system,  which  is  pro- 

What  are  the  f 

characteristics    perly  the  first,  has  all  its  axes  equal,  and  all 

°/ystkemTUlar  its  angles  right  angles.f  The  figures 
which  precede  this  paragraph,  represent 
some  of  its  simpler  forms.  Those  which  follow,  are 
among  its  most  interesting  combinations.  In  the 
last,  the  student  will  be  able  to  select  three  distinct 
kinds  of  surfaces.  One  of  these  sets,  if  enlarged  to 
the  exclusion  of  the  others,  would  produce  a  cube, 

*  The  variations  of  length  and  inclination  of  axis  which  correspond 
to  the  different  systems,  may  be  beautifully  illustrated  to  the  eye  by  a 
wooden  frame  work  movable  at  the  centre  with  threads  connecting 
the  arms. 

f  The  first  and  sixth  systems  are  made  to  change  places  in  the  above 
ai'rangement,  for  the  convenience  of  illustration,  from  the  quartz  crystal. 


CRYSTALS.  283 

another  a  regular  octahedron,  and  a  third  a  dodecahe- 
dron ;  forms  corresponding  to  those  of  the  preceding  line. 


In  view  of  its  simplicity,  the  regular  system  may  be 
regarded  as  a  sort  of  primitive  architecture,  yielding, 
however,  to  no  other  system  in  the  beauty  of  its  forms. 
Under  one  or  the  other  of  these  systems  all  forms  of 
crystals  are  included.  To  each  of  them,  with  the  ex- 
ception of  the  last,  belong  innumerable  sets  of  forms 
according  to  the  degree  of  inequality  or  inclination  of 
the  axes.  Equality  and  rectangular  position  of  the  axes 
being  characteristic  of  the  first  system,  it  is  not  suscep- 
tible of  the  sort  of  variation  which  is  essential  to  pro- 
duce different  sets  of  figures.  But  in  this,  as  in  other 
systems,  the  modification  of  surfaces  may  occur  to  any 
extent. 
„,  ,  ,,  707.  As  the  architect  is  able,  from  some 

bn.ow  now  trie 

formofacrys-  relic  of  a  broken  column,  to  build  up  in 
ferr^ifrom,  imagination  the  temple  of  which  it  formed 
its  angles.  a  part .  as  the  comparative  anatomist  knows 
how,  from  the  fragment  of  a  single  bone  to  reconstruct 
in  imagination  the  perfect  animal  which  possessed  it ; 
so,  from  the  merest  point  of  a  crystal,  its  complete  form 
may  often  be  readily  inferred.  In  proportion  as  a  dou- 
ble pyramid  is  lengthened  out,  the  angles  above  arid 
below  are  rendered  more  acute.  Prom  an  accurate 
admeasurement  of  this  angle  its  whole  shape  may  there- 
fore be  inferred.  Such  admeasurement  of  various  an- 


284 


SALTS. 


gles  is  employed  not  alone  as  a  means  of  inference  of 
perfect  from  imperfect  shapes,  but  as  the  simplest  means 
of  accurate  description.  For,  as  before  stated,  it  is  the 
size  of  the  corresponding  angles  of  a  crystal  which 
form  its  characteristic. 
Have  different  70S.  ISOMORPHISM. — Many  substances 

substances  ever     whi(jh  are  aljke  in  ^  ,mmber  and  arrange. 

Iflv    SGL-iflv  CTlj&m  ^ 

tallineform?  ment  of  their  atoms,  although  these  atoms 
are  different  in  kind,  have  the  same  crystalline  form. 
This  is  the  case  with  common  alum,  and  other  alums 
to  be  hereafter  mentioned.  The  similar  arrangement 
of  atoms  will  be  best  seen  by  inspecting  the  formulas 
which  represent  them.  These  are  given  in  the  appendix. 
The  term  expresses  their  likeness  in  form.  Besides 
this  series  there  are  many  other  isomorphous  groups. 
Give  the  pro-  709.  It  is  to  be  regarded  as  probable, 
babie  reason.  that  faQ  snape  and  size  of  the  molecules 
thus  similarly  composed,  is  exactly  the  same,  and  that 
it  is  for  this  reason  that  they  may  be  used  in  building 
up  crystals  of  the  same  form.  The  different  alums  will 
even  unite  when  they  crystallize,  in  building  up  one 
and  the  same  crystal.  Substances  which  are  thus  si- 
milar in  composition,  and  crystallize  in  the  same  form, 
are  called  isomorphous.  There  are  many  cases  of  simi- 
lar crystalline  form  in  substances  which  are  not  thus 
related  in  other  respects.  Such  bodies  are  not  called 
isomorphous,  notwithstanding  their  identity  of  crys- 
talline form.  Certain  substances  crystallize  in  forms 
belonging  to  two  or  even  three  different  systems,  ac- 
cording to  the  temperature,  or  other  circumstances 
under  which  their  crystallization  occurs.  Such  sub- 
stances are  called  dimorphous  or  trimorphous. 


OXIDES.  285 


OXIDES. 


Define  an  ox-        710.   The  compounds  of  the  metals  with 


terms  ere-    oxygenj  with  tne  exception  of  those  which 
ferent  oxides      have  decided  Iv  acid  properties,  are  called 

distinguished?  _„      J 

oxides.  When  a  metal  unites  with  oxy- 
gen in  several  different  proportions,  forming  different 
oxides,  these  a"re  distinguished  as  protoxide,  deutoxide 
or  binoxide,  tritoxidc  or  teroxide  :  terms  signifying 
first,  second,  and  third  ^oxides.  The  highest  oxide  is 
also  called  peroxide.  An  oxide  containing  three  atoms 
of  oxygen  to  two  atoms  of  metal,  is  called  a  sesquiox- 
ide.  The  names  of  chlorides,  sulphurets,  &c.  are  simi- 
larly modified,  to  indicate  the  proportion  of  chlorine, 
sulphur,  &c.  which  they  respectively  contain.  Com- 
pounds of  non-metallic  substances  with  oxygen  which 
do  not  possess  acid  properties,  are  also  called  oxides. 
There  are,  for  example,  oxides  of  nitrogen  and  phos- 
phorus. 

711.     PROPERTIES     OF     OXIDES.  —  The 

What  is  said 

of  add  and      lower    oxides   are   generally  strong  bases, 
basic  proper-     w^{\e   tne  higher   oxides  exhibit  basic  or 

tics  in  oxides  ? 

acid  properties,  according  to  circumstances. 
Binoxide  of  tin,  for  example,  described  in  a  previous 
chapter,  acts  as  a  base  in  combining  with  sulphuric 
acid  to  form  'a  sulphate,  while,  if  fused  with  potassa,  it 
acts  as  an  acid,  and  forms  a  stannate.  On  account  of 
its  acid  property,  the  binoxide  of  tin  is  also  called  stan- 
nic acid.  The  name  is  derived  from  Stannum,  which 
is  the  Latin  word  for  Tin. 


286  OXIDES. 

712.     FORMATION   OF  OXIDES. — Oxides 

How  are  ox- 
ides formed?      may  be  formed   directly  by  the  union  of 

Give  exam-  oxygen  and  metal,  or,  indirectly,  by  sepa- 
rating them  from  some  salts  which  con- 
tain them.  Thus  oxide  of  copper  may  be  produced 
by  simply  heating  copper  in  the  air ;  or,  by  precipita- 
tion from  the  nitrate,  through  the  agency  of  potassa, 
or,  thirdly,  by  simply  heating  the  nitrate  till  all  the 
acid  is  expelled.  The  oxides  of  tin  and  antimony  are 
also  directly  produced,  by  the  action  of  nitric  acid  on 
the  metals. 

What  is  a  hy-  713.    HYDRATES,    OR    HYDRATED    OXIDES. 

drated  oxide?  Oxides  commonly  combine  in  the  act  of 
precipitation  with  a  certain  proportion  of  water.  The 
compound  thus  formed,  are  called  hydrated  oxides,  or 
simply  hydrates.  The  water  may,  in  most  cases,  be 
separated  from  them  by  heat,  and  the  uncombined 
oxide  thus  obtained. 

714.  CONVERSION    OF  OXIDES. — When 

What  is  said  . 

of  the  conver-  oxides  are  converted  into  chlorides,  sul- 
sionof  oxides?  phuretgj  ^  by  double  decompositions,  to 

be  hereafter  described,  the  chlorides,  sulphurets,  &c., 
correspond  to  the  oxides  from  which  they  are  formed. 
Thus,  protoxide  of  iron  yields  protochloride,  while  ses- 
quioxide  yields  sesquichloride. 

715.  THE  ALKALIES. — The  oxides  of  po- 

Give  some  . 

properties  of  tassmm  and  sodium  are  called  alkalies. 
the  alkalies.  They  are  known  as  potassa  and  soda, 

and  are  commonly  obtained  as  hydrates.  They  are 
white  infusible  substances,  from  which  the  water 
cannot  be  expelled  by  heat.  They  are  soluble  in  water, 


POTASSA.  287 

and  are  the  strongest  of  all  bases.  From  their  destruc- 
tive action  on  animal  matter,  they  are  called  caustic 
alkalies,  and  are  often  distinguished,  by  this  term, 
from  the  carbonates  of  potassa  and  soda. 

POTASSA. 
716.    Potassa  is  prepared   from    wood 

What  is  the 

source  of  po-     ashes.     The  ley  obtained  from  these  be- 
ing evaporated  to  dryness,  the  mass  which 
remains  is  the  crude  potash  of  commerce.     This,  when 
purified,  becomes  pearlash. 

How  is  potassa  717.  CAUSTIC  POTASSA. — Commercial 
prepared?  potash  and  pearlash  are  both  carbonates 
of  potash,  from  which  the  carbonic  acid  must  be 
removed,  in  order  to  produce  potassa  itself.  This  is 
done  by  a  milk  of  slaked  lime.  A  solution  of  potash, 
in  at  least  ten  parts  of  hot  water,  or  a  hot  ley,  made 
directly  from  wood  ashes,  should  be  employed  in  the 
experiment.  To  this,  the  milk  of  lime  is  added,  little 
by  little,  the  solution  boiled  up  after  each  addition, 
and  then  allowed  to  settle.  If,  after  settling,  a  por- 
tion of  the  clear  liquid  is  found  no  longer  to  effervesce 
on  the  addition  of  an  acid,  it  is  sufficient  evidence 
that  all  the  carbonic  acid  has  been  removed  by  the 
lime,  and  the  process  is  completed.  This  must  be  as- 
certained by  trial.  About  half  as  much  lime  as  pot- 
ash will  be  required  in  the  process.  Caustic  soda  is 
similarly  made  from  the  carbonate  of  soda. 

718.     The  boiling  in  the  above  process 

Give  a  modi- 

fication  of  the  may  be  omitted,  if  the  mixture  be  fre- 
above  method.  quent]y  shaken  up,  during  several  days. 


288  OXIDES. 

This  modification  of  the  method  is  much  the  most 
convenient  for  the  production  of  caustic  al- 
kalies in  small  quantities.  Solutions,  useful 
for  a  variety  of  chemical  purposes,  are  thus 
obtained,  and  should  be  preserved  for  use. 
They  may  be  converted  into  solids,  by 
evaporation,  and  the  solid  thus  obtained  fused 
and  run  into  moulds.  The  commercial  caustic 
potassa,  occurring  in  slender  sticks  of  white 
or  grey  color,  is  thus  produced. 

719.  AFFINITY  OF  POTASSA  FOR  WATER. 

How  can  the 

affinity  of  po-     Ordinary  potassa,  as  before  stated, 

is  a  hydrate-  But  its  affinity  for 

water,  is  by  no  means  yet   satis- 
fied in    this    form.      If  exposed    in  an  open 
vessel,  it  rapidly  attracts  moisture    from    the 
air.     It  often  dissolves,  in  the  course  of  a  few  days,  in 
the  water  thus  obtained. 

720.  DECOMPOSITION  BY   POTASSA.  —  Po- 

What  is  said  . 

of  the  decom-  tassa  added  to  the  solution  of  almost 
Ps°aitsTypfo-  any  salt>  occasions  a  precipitate.  The 
tassa?  potassa  takes  the  acid,  and  precipitates  the 

insoluble  base.  If  the  experiment  be  made  with  an 
ammonia  salt,  the  base  being  volatile,  passes  off  into 
the  air.  Experiments  may  also  be  made  with  green, 
blue,  and  white  vitriols,  which  are,  respectively,  sul- 
phates of  iron,  copper,  and  zinc.  , 

721.  CLEANSING   AND   CAUSTIC    PROPER- 
«EB  OF  PoxAssA.-If  soiled  rags  be  boiled 


perties  of  po-    with  a  dilute  solution  of  potassa,  they  will 
be  thoroughly    cleansed   by  the    process. 


POTASSA.  289 

The  potassa  unites  with  the  acid  of  the  grease  con- 

tained in  the  cloth,  and  thus  makes  it  soluble  in  water. 

722.     ACTION    OF    POTASSA    ON    ANIMAL 

What  is  the 

action  of  po-  MATTER.  —  Potassa  is  extremely  destructive 
^al  matter  />"  of  animal  matter.  It  readily  dissolves  the 
skin,  as  may  be  proved  by  rubbing  a  little 
between  the  fingers.  If  applied  in  sufficient  quantity. 
it  destroys  the  vitality  of  the  flesh.  It  is  often  used 
for  this  purpose  by  surgeons. 

723.  EFFECT  ON  VEGETABLE    COLORS.  — 

How  does  po- 

tassa affect  vc-    Vegetable   blues    which   have    been    pre- 
getabie  colors?    viously  reddened  by  acid,  are  restored  to 

their  original  color  by  the  action  of  potash  and  other 
alkalies.  The  blue  pigment  called  litmus  is  the  one 
most  readily  obtained.  In  preparation  for  the  exper- 
iment it  is  infused  in  hot  water  The  transformation 
from  blue  to  red,  and  vice  versa,  may  be  repeated  as 
often  as  desired,  by  the  alternate  addition  of  acid  and 
alkali.  Paper  soaked  in  the  red  and  blue  liquids 
forms  the  test-paper  of  the  chemist.  It  is  used  to  in- 
dicate the  presence  of  smaller  quantities  of  acid  and 
alkali  than  could  be  recognized  by  the  taste.  An  extract 
of  purple  cabbage  leaves,  or  the  leaf  itself,  may  be 
used  in  the  above  experiment.  In  this  case,  the  change 
of  color  by  alkalies  is  from  red  to  green. 

724.  PROPERTIES  OF   SODA.  —  The  prop- 
of     erties  of  soda,  are  very  similar  to  those  of 


potassa,  as  above  described. 
13 


290  OXIDES. 


OXIDE  OF  AMMONIUM. 
725.         FORMATION. — When    hydrated 

WJiatissaid  .  . 

of  oxide  of  sulphuric  acid  combines  with  ammonia, 
ammonium?  tne  water  which  it  contains  is  regarded 
as  converting  the  ammonia  into  oxide  of  ammonium, 
with  which  the  acid  then  combines.  The  action  of 
other  hydrated  acids  is  the  same.  In  naming  the  cor- 
responding salts,  the  oxide  of  ammonium  is  called 
ammonia.  Thus,  the  compound  with  sulphuric  acid, 
is  called  sulphate  of  ammonia.  It  is  to  be  borne  in 
mind,  that  oxide  of  ammonium  of  such  salts,  contains 
an  atom  of  water,  in  addition  to  the  constituents  of 
ammoniacal  gas. 

OXIDE  OF  CALCIUM. 

How  is  lime  726.   LIME. — Lime  or  oxide  of  calcium 

obtained?  is  best  obtained  by  heating  chalk,  marble 
or  limestone.  These  are  all  carbonates  of  lime.  Under 
the  influence  of  a  high  temperature,  the  tendency  of 
the  carbonic  acid  to  assume  the  gaseous  form  is  so 
increased,  that  the  chemical  affinities  of  the  base  are 
overcome.  The  carbonic  acid  escapes,  leaving  the  caus- 
tic lime  behind.  This  is  the  process  of  the  ordinary  lime 
kiln.  The  superior  strength  of  potassa  and  soda,  as 
bases,  is  illustrated  by  the  fact  that  the  carbonic  acid 
cannot  be  removed  from  them  through  the  agency  of 
heat. 

TO*  ,  •   ,  ^27.   HYDRATE  OF  LIME. — SLAKED  LIME. 
What  is  hy- 
drate of  *  When  water  is  added  to  lime,  one  equiva- 
^^me?  jent  jmme(jiate]y  combines  with    it,   and 


LIME.  291 

forms  a  hydrate.  The  hydrate,  like  that  of  potassa,  is 
dry,  although  it  contains  a  large  portion  of  combined 
water.  As  the  water  thus  becomes  solid  in  the  com- 
pound, its  latent  heat  is  given  off  to  the  air  or  sur- 
rounding objects.  The  employment  of  heat  thus  pro- 
duced for  culinary  operations  has  been  recently  sug- 
gested. If  the  process  of  slaking  be  conducted 
under  a  tumbler,  with  a  slight  surplus  of  water,  steam 
will  be  produced.  On  lifting  the  tumbler,  it  will  be- 
come visible  by  its  condensation  into  vapor. 

728.     IGNITION    BY    LIME.  —  The    heat 

How  may  gun- 

powder be  iff-  thus  produced,  is  often  sufficient  to  ignite 
Ik^en^of  gun-powder.  It  should  be  sprinkled  on 
lime?  the  mass,  and  kept  dry  while  the  slaking 

proceeds.  Warm  water  and  well-burned  lime  should 
be  employed  in  the  experiment. 

729.    ACTION  OF  THE  AIR.  —  If  lime   is 

What  is  the 

action  of  the     exposed  to  the  action  of  the  air,  it  gradu- 

aironlime?  cart)Onic     acid     and 


water,  and  becomes  converted  into  a  mixture  of  hydrate 
and  carbonate.  It  is  then  called  air-slaked  lime.  By 
sufficiently  long  exposure  the  conversion  into  carbo- 
nate is  complete. 

730.  LIME  IN  MORTAR.  —  Ordinary  mortar 
mortar  har-  is  a  mixture  of  sand  and  lime.  It  hardens 
not  simply  by  drying,  but  by  the  absorp- 
tion of  carbonic  acid  from  the  air.  A  compound  of 
hydrate  and  carbonate  of  lime,  possessed  of  great  hard- 
ness, is  thus  produced.  A  gradual  combination,  also 
takes  place  between  the  silica  and  the  lime,  which 
binds  the  two  constituents  still  more  firmly  together. 


292  OXIDES. 

731.    HYDRAULIC    CEMENT. — If,   in   the 

WJiat  is  liy- 

drauic  ce-  preparation  of  lime,  a  limestone  is  used 
which  contains  a  certain  proportion  of 
clay,  a  double  silicate  of  alumina  and  lime  is  produced. 
The  compound  has  not  alone  the  property  of  combi- 
ning with  water,  like  ordinary  lime,  but  of  becoming 
extremely  hard  and  insoluble  in  the  process.  Such  a 
lime  is  called  hydraulic  cement,  and  is  used  for  building 
under  water.  Silica,  magnesia,  and  some  other  sub- 
stances impart  the  same  property  to  lime. 

ALUMINA,  MAGNESIA,  (fee. 

Whatisalu-  732.  ALUMINA,  &c. — Alumina,  so  named 
mina'  from  the  corresponding  metal,  is  insoluble, 

and  is  called  an  earth.  It  is,  like  the  peroxide  of  iron, 
a  sesquoxide,  containing  three  atoms  of  oxygen  to  two 
of  metal.  Natural  alumina,  colored  blue,  is  called  sap- 
phire. Colored  red,  it  forms  the  oriental  ruby.  The 
topaz  and  the  emerald  are  also  compounds  containing 
the  same  oxide.  Baryta,  strontia,  lime  and  magnesia, 
are  regarded  as  standing  midway  between  the  earth 
alumina  and  the  alkalies,  and  are  called  alkaline  earths. 
They  are  more  or  less  soluble,  and  possess  the  general 
properties  of  the  alkalies,  in  a  diminished  degree. 
Magnesia  is  sometimes  classed  as  an  earth. 

733.     OTHER  METALLIC    OXIDES. — The 

What  are  the 

properties  of     remaining  metallic  oxides   are  powders  of 
lalh°foxiL%    different   colors.     Most  of  them  are  insol- 
uble.     The    more   important   have    been 
already   noticed,  in   the    Chapter  on   Metals.      Their 


OXIDES.  293 

hydrates  may  be  obtained  by  precipitating  solutions 
of  their  salts  with  potassa,  soda,  or  ammonia.  The  hy- 
drate of  the  oxide  of  copper,  and  peroxide  of  iron, 
may  serve  as  examples.  The  former  is  blue  and  the 
latter  a  reddish  brown. 

734.  The  hydrated  oxides  of  nickel,  co- 
ted  oxid™  dis-    bait,  tin  and  copper,   produced  from  soliu 
soiveinam-      tion  of  these  metais    by  the  addition  of 

moma  ?  J 

ammonia,  are  again  re-dissolved  in  an 
excess  of  ammonia.  That  of  copper  dissolves  with  a 
beautiful  blue  color,  which  is  conclusive  evidence  that 
the  liquid  with  which  the  experiment  is  made  contains 
copper  in  solution. 

735.  USES.  —  Oxide  of  magnesium    or 

Give  the  uses 

of  some  of  the  magnesia,  and  mercury,  among  others,  are 
oxide*  ?  used  in  medicine,  and  white  oxide  of  zinc, 

as  a  paint.  Litharge  or  protoxide  of  lead  is  employed 
in  making  flint-glass  and  varnishes.  Red  lead  is  used 
as  a  paint.  Oxide  of  bismuth  is  employed  as  a  cos- 
metic. 

736.  Oxide  of  manganese  is  used  to 

C°lor       laSS      U1'le    aild    Vi°let       Oxide  °f 


glass  by  the       cobalt,  to  color  it  blue  :  oxides  of  copper, 

oxide  of  man- 

ganese, cobalt,  and  chromium,  to  impart  a  green  color  to 
CdxpC&c  7°n'  £lass  and  Porcelaitl  j  peroxide  of  iron, 
to  give  it  a  yellowish  red,  and  protoxide,  a 
bottle-green.  Sub-oxide  of  copper  gives  to  glass  a 
beautiful  ruby  red.  Silver  and  antimony  are  employed 
to  produce  different  shades  of  yellow  and  orange.  Vi- 
olet and  rose  color,  are  obtained  by  means  of  the  purple 
of  cassius,  a  beautiful  purple  precipitate,  containing 


294  CHLORIDES. 

tin  and  gold,  and  obtained  by  adding  protochloride  of 
tin  to  a  gold  solution. 

737.  GLASS  STAINING. — The  effect  of 
effects  be  illua-  oxides,  above  mentioned,  in  coloring  glass, 
trated?  mav  ^Q  jnustrated  by  fusing  them  into  a 

borax  bead.     The  bead  is  to  be  formed  with  the 


aid  of  the  blow-pipe,  in  a  loop  of  platinum  wire. 
In  the  absence  of  such  wire,  the  borax  glass 
may  be  made  upon  the  surface  of  a  pipe  bowl.  In- 
stead of  employing  the  oxide,  it  is  generally  more 
convenient  to  moisten  the  bead  with  a  very  small 
quantity  of  a  solution  of  the  metal.  In  order  to  obtain 
good  colors,  the  quantity  of  coloring  material  employed 
must  be  very  small. 

738.  For  staining  glass  and  porcelain  su- 
and  porcelain    perficialiy,    a   colored   and    easily   fusible 


SlaSS  1S  fil>St  PrePared  with  borax     Or  S0me 

analogous  material.  This  being  ground 
up  and  applied  as  a  paint,  is  afterward  baked  into 
the  surface.  Several  of  the  oxides  mentioned  in  a  pre- 
ceding paragraph  are  thus  employed. 

CHLORIDES. 
739.  DESCRIPTION.  —  The  chlorides  are, 

Describe  some 

of  the  proper-    for  the  most  part,  soluble   salts,   of  colors 


corresponding  to  the  solutions  of  the  metals 
from  which  they  are  produced.  Common 
salt  may  stand  as  a  type  of  the  class.  The 
chloride  of  silver,  subchloride  of  mercury  or 
calomel,  are  insoluble,  and  the  chloride  of  lead 
but  slightly  soluble  in  water. 


CHLORIDES.  295 

740.   PREPARATION.  —  Chlorides  may  be 

How  are  chlo-  ,     ,         .  .  .,      ,  ,  .       , 

rides  made        made  by  the  action  of  chlorine  or  hydro- 


chloric  acid  on  the  metals.  The  combus- 
tion of  antimony  in  chlorine  gas,  the  solu- 
tion of  gold  in  aqua  regia,  and  that  of  zinc  in  hydro- 
chloric acid  are  examples.  The  chemical  action  in  each 
of  these  cases  has  been  explained  in  previous  chapters. 
The  solutions  being  evaporated,  the  chlorides  are  ob- 
tained in  the  solid  form.  The  solution  of  zinc  in  hy- 
drochloric acid  is  a  case  of  single  elective  affinity: 
the  metal  elects  or  chooses  the  chlorine. 

741.  Chlorides  may  also  be  formed  by 

How  are  chlo- 

rides produced  the  action  of  hydrochloric  acid  on  oxides. 
from  oxide*?  Thug  common  salt  or  chloride  of  sodium 

may  be  made  by  mixing  hydrochloric  acid  and  soda. 
The  hydrogen  of  the  acid  and  the  oxygen  of  the  soda 
unite  to  form  water,  while  the  chlorine  of  the  acid  and 
the  metal  sodium  unite,  to  form  the  chloride.  This  is 
a  case  of  double  decomposition,  resulting  from  double 
elective  affinity.  The  chloride  commonly  corresponds 
to  the  oxide  from  which  it  is  produced.  Thus  soda, 
which  is  a  protoxide,  yields  common  salt,  which  is  a 
protochloride.  Again,  sesquioxide  of  iron,  containing 
three  atoms  of  oxygen  to  one  of  metal,  yields  susqui- 
chloride  of  iron  containing  the  same  proportion  of  chlo- 
rine. 

How  are  the  ^2.  The  insoluble  chlorides  may  be  ob- 
insolubie  chlo-  tained  directly  in  a  solid  form  by  a  similar 

rides  obtained  „ 

directly  in  a,  double  decomposition.  Thus,  chloride  of 
solid  form?  sodium  and  oxide  of  silver  in  solution, 


296  CHLORIDES. 

yield,  when  mixed,  a  precipitate  of  chloride 
of  silver ;  newly-formed  oxide  of  sodium  or 
soda  remains  in  solution.  The  latter  unites 
with  the  acid  originally  employed  to  dissolve 
the  oxide  of  silver.  This  is  commonly  nitric 
acid. 

743.    CHLORIDE    OF    SODIUM. — COMMON 

From  what  _.  i       •       /•          i      • 

sources  is  com-  SALT. — Common  salt  is  found  in  great 
Obtained?  abundance  in  Poland  and  other  countries, 
as  Rock  salt,  which  is  regularly  mined  like 
coal.  It  is  also  obtained  by  evaporating  the  water  of 
the  sea  or  salt  springs,  in  the  sun  or  by  artificial  heat. 
When  the  salt  water  is  boiled  down,  the  salt  separates 
in  crystals,  while  the  impurities  remain  in  the  small 
portion  of  liquid  which  is  not  evaporated.  These  con- 
sist principally  of  chloride  of  magnesium  and  other 
salts.  Contrary  to  the  general  rule,  salt  is  equally  solu- 
ble in  cold  and  hot  water. 

744.    When    salt    is   to   be   made   from 

How  is  salt  ,  .        .     . 

produced  from  water  which  contains  it  in  very  small  pro- 
portion,  it  is  a  frequent  practice  in  Europe, 
to  pump  the  weak  brine  to  the  top  of  large 
heaps  of  brush,  and  allow  it  to  trickle  through  them. 
The  object  of  the  method  is  to  produce  a  large  evapo- 
rating surface.  The  air,  as  it  passes  through  the  heaps, 
carries  away  a  large  part  of  the  water,  and  leaves  the 
salt  behind.  The  strong  brine  which  is  collected  below, 
is  then  boiled  down,  as  before  described.  The  annual 
produce  of  the  salt  spring  at  Syracuse,  New  York,  ex- 
ceeds 5,000,000  bushels. 


CHLORINE.  297 

745.  Beautiful  crystals  of  common  salt 

How  may  crys-  .       .       ..        '  ,       .. 

tals  of  salt  be  may  be  obtained  by  gradually  evaporating 
obtained?  a  saturale(j  solution.  This  will  be  accom- 
plished by  keeping  it  for  some  time  moderately  warm, 
on  a  stove  or  in  the  sun.  The  crys- 
tals are  shaped  as  represented  in  the 
figure,  and  are  made  of  innumerable 
smaller  cubes,  which  build  them- 
selves regularly  upon  the  edges  as  the  larger  crystals 
sinks  little  by  little  into  the  solution. 

746.  USES  OF  COMMON  SALT. — The  use 

How  does  salt 

act  to  preserve  of  common  salt  in  preserving  the  flesh  of 
flesh?  animals  from  decay,  depends  in  part  on 

the  fact  that  it  extracts  from  the  flesh  a  large  propor- 
tion of  water.  It  thus,  to  a  certain  extent,  dries  them. 
This  action  will  be  immediately  observed  if  a  little 
salt  be  sprinkled  upon  flesh.  It  will  speedily  draw 
out  the  juices  of  the  meat,  and  itself  disappear,  by  dis- 
solving in  them. 

ffowmucksait        747'   SEA  WATER.— Every  pound  of  sea 

is  contained  in  water  contains  from  one-half  to  five- 
sea  water  ?  in 

the  water  of  eighths  of  an  ounce  of  salt.  The  greater 
theDeadSea?  part  of  thig  is  chloride  of  sodium  or  com- 
mon salt.  The  water  of  the  Dead  Sea  contains  a 
much  larger  proportion,  and  is  more  than  an  eighth 
part  heavier  than  pure  water.  Owing  to  its  greater 
density,  a  muscular  man  floats  breast  high  in  it  without 
the  least  exertion.  Fresh  eggs,  which  sink  in  sea 
water,  float  in  that  of  the  Dead  Sea,  with  one-third  of 
their  length  above  the  surface. 

13* 


298  CHLORIDES. 

748.  CHLORIDE  OF  LIME. — BLEACHING 

On  what  does 

the  value  of  POWDER. — The  commercial  article  of  this 
?  name  is  PrePared  bY  passing  chlorine  gas 
over  lirne.  It  is  a  white  powder,  with  an 
odor  similar  to  that  of  .chlorine  gas.  Its  value  depends 
on  the  fact  that  the  gas  is  thus  brought  into  a  solid 
form,  and  made  capable  of  transportation.  It  may  be 
released  again  by  the  simplest  means,  to  be  used  as  a 
bleaching  and  disaffecting  agent.  The  addition  of  an 
acid,  as  has  been  seen  in  the  chapter  on  chlorine,  is  all 
that  is  necessary  to  effect  this  object.  It  occurs,  in- 
deed, spontaneously  in  the  moistened  powder,  through 
the  action  of  the  carbonic  acid  of  the  air. 

749.  ILLUSTRATION. — To    illustrate  its 

How  may  its 

properties  be  bleaching  power,  a  strip  of  calico  may  be 
illustrated?  soaked  in  a  solution  of  the  chloride,  and 
then  in  acid  water.  Nascent  chlorine  is  thus  liberated  in 
the  fibre  of  the  cloth,  and  is  more  effectual  than  if 
otherwise  applied. 

750.   FORM  OF  COMBINATION. — The  che- 

How  are  its  ...  i  •   -, 

elements  com-  mical  action  which  occurs  in  the  formation 
lined?  of  chloride  of  lime  is  as  follows.  The 

chlorine  combines  with  both  constituents  of  the  lime 
forming  with  its  metal  chloride  of  calcium,  and  with  its 
oxygen,  hypochlorous  acid.  This  acid  combines  as  it 
is  produced,  with  another  portion  of  lime,  forming  a  salt. 
Bleaching  powder  is  therefore  a  mixture  of  chloride  of 
calcium  and  hypochlorite  of  lime,  with  a  certain  pro- 
portion of  lime  still  uncombined.  The  name  chloride 
of  lime  has  no  chemical  propriety.  The  mixture  is, 
practically,  chlorine  and  lime,  for  as  soon  as  an  acid  is 


CHLORIDE    OF    ALUMINIUM.  299 

added,  all  of  the  original  lime  is  re-formed  and  chlorine 
is  evolved. 

751.    CHLORIDE    OF    ALUMINIUM.  —  This 

How  is  chlo- 

ride of  alumi-  salt  is  of  peculiar  interest  and  importance, 
"pared*?  *'  *n  v*ew  °^  *ts  employment  in  the  prepara- 
tion of  the  new  metal  aluminium.  It  is 
prepared  by  heating  alumina  at  the  same  time  with  car- 
bon and  chlorine.  The  alumina  is  torn  asunder,  as  it 
were,  by  the  affinities  which  are  thus  brought  into  play. 
The  carbon  takes  its  oxygen  and  passes  off  with  it  as  car- 
bonic oxide,  while  the  chlorine  takes  the  metal  and  es- 
capes with  it  as  volatile  chloride  of  aluminium.  The 
carbon  in  the  process  is  supplied  by  coal  tar.  The 
process  is  conducted  in  iron  retorts,  the  materials  hav- 
ing been  previously  ignited  together  before  their  intro- 
duction. 

How  is  it  pu-  75%-  The  chloride  is  impure,  from  the 
rifted?  presence  of  volatile  sesquichloride  of  iron. 

This  is  separated  by  leading  the  uncondensed  vapors 
over  highly  heated  points  of  iron.  The  iron  has  the 
effect  of  removing  part  of  the  chlorine  from  the  ses- 
quichloride of  iron  and  reducing  it  to  a  non-volatile 
protochloride.  It  is  thus  stopped  in  its  course,  while 
the  chloride  of  aluminium  passes  on  unaffected.  It  con- 
denses in  the  cooler  part  of  the  apparatus,  in  the 
form  of  colorless  transparent  crystals. 

753.     COLORED    FLAMES.  —  A  series    of 

What  is  said  . 

of  colored         beautiful  name  experiments  may  be  made 

flames? 


assumes  different  colors  according  to  the  chloride  em- 
ployed.    Chloride  of  sodium    or  common   salt,  gives 


300  SALTS. 

a  yellow  ;  chloride  of  potassium,  violet  ; 
chloride  of  calcium,  orange  ;  chloride  of 
barium,  yellow ;  chloride  of  copper,  blue. 
Instead  of  the  chlorides,  other  soluble 
salts  may  be  employed  with  the  addition  of  a  little  hy- 
drochloric acid.  £,  beautiful  green  may  be  obtained 
from  a  copper  coin  moistened  with  strong  nitric  acid, 
with  the  use  of  alcohol  as  before.  The  colors  of  fire- 
works are  similarly  produced  by  the  addition  of  the 
above  and  certain  other  salts. 

754.     OTHER    CHLORIDES. — The    other 

What  is  said        i  i      •  j  /• 

of  other  ckio-  chlorides  are  not  of  sufficient  general  in- 
terest to  be  here  particularly  described.  Cor- 
rosive sublimate,  the  uses  of  which  are  mentioned  in 
the  chapter  on  Mercury,  is  a  chloride  of  this  metal. 
Calomel  is  a  subchloride  of  the  same  metal. 


IODIDES,  BROMIDES  AND  FLUORIDES. 

755.  The    iodides    and    bromides    are 

What  is  said 

of  the  iodides  classes  of  salts  analogous  to  the  chlorides. 
andbromides?  Those  of  potassium,  used  in  medicine  and 
in  photography,  are  the  most  important. 

756.  DETECTION    OF  T<roioo<r  IODINE. — 
JTowistheblue                      -r'  i    1.1          •  i    -,  -, -,- 

iodide  of  A  beautiful  blue  is  prepared  by  adding  a 
pared  r6'  little  cnlorme  water  and  starch  paste  to  a 
solution  of  iodide  of  potassium.  The 
chloride  sets  iodine  at  liberty,  which  then  combines 
with  starch  to  form  the  blue  compound.  By  this  test 
iodine  can  be  detected  in  a  liquid  which  contains  but  a 


IODIDES    AND    BROMIDES.  301 

millionth  part  of  this  element.  By  the  substitution  of 
bromide  of  potassium  in  the  experiment,  an  orange 
color  is  produced. 

How  is  this  757.  TEST  FOR  CHLORINE  AND  IODINE. — 

experiment        rp^e    experiment   may  also    be    made  by 

employed  as  a  .  '  . 

test  for  chlo-  moistening  a  slip  of  paper  with  starch  and 
iodide  of  potassium,  and  holding  it  in  an 
atmosphere  containing  a  little  chlorine  gas. 
An  extremely  small  quantity  of  chlorine  is 
thus  indicated,  and  the  prepared  paper  thus 
becomes  a  test  for  chlorine.  Such  paper  is 
also  used  to  show  the  presence  of  ozone  in 
the  air. 

758.    CHANGE  OF  COLOR  BY  HEAT. — By 

What  is  said  .  .  .  ' 

of  the  iodide  of  mixing  solutions  of  iodides  of  potassium 
and  corrosive  sublimate  or  chloride  of  mer- 
cury, a  beautiful  scarlet  iodide  of  mercury  is  produced. 
On  heating  the  dried  precipitate  it  becomes  yellow. 
The  experiment  is  best  made  with  two  watch  glasses. 
The  iodide  is  heated  in  the  lower  one  and  collects  by 
sublimation,  with  changed  color,  in  the  upper. 

What  effect  is  759.     CHANGE    OF      COLOR     BY      TOUCH. 

produced  by       On  touching  the  yellow  incrustation  with 

touching  the  .  .  ,.  ,,  , .        , 

yellow  incrus-  the  point  of  a  needle,  it  is  immediately 
tation?  stained  scarlet  at  the  point  of  contact.  The 

color  gradually  spreads,  as  if  it  were  a  contagious  dis- 
ease, through  the  whole  mass,  until  every  particle  has 
regained  its  original  scarlet.  This  experiment  fur- 
nishes a  very  remarkable  instance  of  change  of  an  im- 
portant property  without  change  of  composition.  As 


302 


SALTS. 


the  change  of  color  proceeds,  the  small  scales  of  which 
the  yellow  iodide  is  composed  break  up  into  octa- 
hedrons. The  change  of  color  is  regarded  as  a  conse- 
quence of  the  re-arrangement  of  atoms,  which  produces 
the  change  of  form. 

FLUORIDES. 

What  is  said  760.  FLUOR-SPAR. — The  fluorides,  with 
of 'fluor-spar  ?  fae  exception  of  those  of  the  alkalies,  are 
for  the  most  part,  white  insoluble  compounds.  The 
only  one  of  especial  interest,  is  the  beautiful  mineral 
knoivn  as  fluor-spar.  This  mineral  is  a  fluoride  of 
calcium.  It  is  found  of  white,  green,  purple 
and  rose  color,  crystallized  in  regular  cubes 
or  octahedrons.  Hydrofluoric  acid,  which  has 
the  remarkable  property  of  etching  glass,  as 
before  described,  is  prepared  from  it. 

SULPHURETS. 

Define  a  sul-          ?^-  The  compounds  of  the  metals  with 
phuret.  sulphur  are  called  sulphides  or  sulphur ets. 

They  are  of  various  colors,  and,  for  the 
most  part,  insoluble.  Iron  pyrites,  and  ga- 
lena or  sulphuret  of  lead,  are  examples. 
The  figure  represents  a  crystal  of  magnetic  pyrites, 
which  is  one  of  the  sulphurets  of  iron.  The  form  be- 
longs to  the  sixth  or  hexagonal  system. 

762.    PREPARATION. — Most  of   the  sul- 

How  are  sul- 
phurets gene-     phurets  may  be  produced  by  adding  hydro- 

paaredT~         sulphuric  acid  to  solutions  of  the  different 
metals  or  their  salts.     Sulphur  and  metal 


SULPHURETS.  303 

unite  and  precipitate,  while  the  hydrogen  and  oxygen, 
previously  combined  with  them,  form  water. 
Mention  the          763.    The  sulphuret  of  zinc  is  white  ; 
colors  of  some    tnat  of  arsenic  yellow  ;  and  that  of  anti- 

of  the  sulphu-  '   J 

rets.  mony,  orange.     The  remainder  of  the  in- 

soluble sulphurets  are  black.  Solutions  of 
white  vitriol,  arsenious  acid,  and  tartar  emetic 
may  be  used,  as  above  directed,  to  produce  sul- 
phurets of  zinc,  arsenic  and  antimony.  If 
the  zinc  precipitate  should  be  colored,  it  is 
owing  to  the  presence  of  iron  in  the  salt,  as 
impurity.  Blue  vitriol  may  be  employed  to  produce 
black  sulphuret  of  copper. 

764.  The  sulphurets  of  ammonium,  po- 

What  is  said 

of  the  sulphu-  tassmm  and  sodium,  cannot  be  precipitated 
raika/ielh?e  by  this  Process-  Being  soluble,  they  re- 
main in  the  liquid.  Solutions  of  the  caus- 
tic alkalies  are  to  be  used  in  preparing  them.  The  so- 
lutions of  these  sulphurets  are  useful,  as  they  may,  in 
many  cases,  be  substituted  with  advantage  for  hydro- 
sulphuric  acid,  in  precipitating  sulphurets  from  solutions 
of  other  metals.  Certain  other  sulphurets  are  soluble, 
and  do  not  precipitate,  as  will  be  seen  from  the  table 
in  the  Appendix. 

765.  LIVER  OF  SULPHUR. — There  are  a 

What  is  liver  f        .  f 

of  sulphur?      number  of  sulphurets  of  potassium,  con- 
jj  u  pre"    taining  each  a  different  proportion  of  sul- 
phur.    That  which  contains  five  atoms  of 
sulphur,  to  one   of  metal,  is  called,  from  its  peculiar 
color,  liver  of  sulphur.    It  is  prepared  by  boiling  flowers 
of  sulphur  in  a  strong  solution  of  potash.     It  may  also 


304  SALTS. 

be  made  by  fusion  of  the  same  materials.  The  proto- 
sulphuret  can  be  made  from  the  sulphate,  by  reduction 
with  hot  carbon.  Certain  other  soluble  sulphurets  may 
be  prepared  in  the  same  manner. 

766.  MILK  OF  SULPHUR. — This  form  of 

How  is  milk  of  ,  .  .  . 

sulphur  pre-  sulphur,  like  that  just  mentioned,  is  used 
pared?  ^  me(jicine.  It  may  be  prepared  from  a 

solution  of  the  liver  of  sulphur,  by  the  addition  of  an 
acid.  The  latter  combining  with  the  potassa,  the  sul- 
phur is  precipitated  in  a  state  of  the  finest  division, 
giving  to  the  liquid  the  appearance  of  milk. 

767.  OTHER   SULPHURETS. — The   natu- 
of  the  other       ral  sulphurets  have  colors   different   from 
sulphurets?       ^Q  similar  compounds  when  produced,  as 
above,  by  precipitation.     Thus,   the  natural  sulphuret 
of  lead,  or  galena,  has  the  color  of  the  metal  ;  that  of 
mercury  is  red,  and  is  called  cinnabar  ;  that  of  zinc, 
called  zinc  blende,  and  by  miners,  black  jack,  is  of  dif- 
ferent shades — brown,  yellow  and  black.     The  precipi- 
tated sulphuret  of  mercury  turns  red  by  sublimation, 
and  in  this  state  forms  the  familiar  pigment  called  ver- 
milion.     Sulphuret    of   iron,   which    is   employed   in 
making  hydrosulphuric  acid,  may  be  prepared  by  hold- 
ing a  roll  of  sulphur  against  a  rod  of  iron    previously 
heated  to  whiteness.     This  may  be  readily  done  in  any 
blacksmith's  shop.     The  fused  sulphuret  falls  in  glo- 
bules from  the  surface  of  the  iron. 


SULPHATES.  305 

SULPHATES. 

768.  The  sulphates,  with  the  ex- 

What  is  said 

of  the  color      ception    of   those    of   the    alkaline 

are     f°r   the    mOSt 


ble  salts,  of  colors  corresponding  to 
the  solutions  of  the  corresponding  metals.     The 
figure  represents  a  crystal  of  gypsum.     The  form 
longs  to  the  fourth  system. 

769.   PREPARATION.  —  The  sulphates  are 

How  are  the  .,,,.,         ,         ,        ,. 

sulphates  produced  either  by  the  direct  combination 
of  sulphuric  acid  with  the  proper  oxide,  or 
by  its  action  on  the  metals.  The  latter  has  been  already 
particularly  described  in  the  section  on  sulphuric  acid. 
They  are  also  sometimes  formed  in  nature,  by  the 
action  of  the  air  on  sulphurets.  In  this  action,  the 
metal  is  converted  into  oxide,  and  the  sulphur  into  acid, 
which  together  form  the  sulphate.  Green  vitriol  is 
sometimes  thus  formed  in  soils,  from  sulphuret  of  iron 
ox  fool's  gold. 

What  ix  gyp-  ?70.      SULPHATE    OF     LIME.  -  GYPSUM.  - 

sum?  This  is  a  white,  soft   mineral,  occurring 

abundantly  in  nature.  The  finer  kinds  are  known  as 
alabaster.  Finely  ground,  it  is  employed  extensively 
as  a  fertilizer  of  the  soil  under  the  name  of  plaster. 
Plaster  of  Paris  is  produced  by  heating  gypsum  until 
its  water  is  expelled.  The  plaster,  when  pulverized, 
has  the  property  of  setting  with  water,  or,  in  other 
words,  forming  a  hard  coherent  mass. 

771.    PLASTER    CASTS.  —  These  are   pro- 

How  are  plas-  . 

ter  casts  pro-  duced  by  reducing  the  burned  or  powdered 
duced?  gypsum  to  the  consistence  of  cream,  with 


306  SALTS. 

water,  and  then  pouring  it  into  moulds.  A  coin  may 
be  copied  by  pouring  such  a  paste  into  a  small  paper  box 
containing  the  coin.  Two  parts  of  ordinary  ground 
gypsum,  heated  moderately  until  vapor  ceases  to  escape, 
and  then  mixed  with  one  part  of  water,  form  a  good 
proportion.  The  heat  should  not  be  carried  very  far 
beyond  that  of  boiling  water,  or  the  plaster  refuses  to 
set. 

772.  The  hardening  of  the  plaster  part 
ter  casts  hard-    takes  place  very  rapidly.     It  is  owing  to 

the  re-combination  of  the  material  with 
water.  The  water  thus  absorbed  exists  in  a  solid  form 
in  the  compound,  as  in  other  salts. 

773.  ALUMINATED  PLASTER. — Harder  and 

What  is  alu- 

minatedplas-  better  casts,  more  nearly  resembling  mar- 
ble, are  made  by  steeping  the  burned  gyp- 
sum for  six  hours  in  strong  alum  water,  and  then  re- 
heating it  at  a  higher  temperature.  After  being  again 
pulverized,  it  may  be  used  like  ordinary  plaster,  but 
requires  more  time  to  harden. 

774.  SULPHATE    OF    SODA. — GLAUBER'S 

Describe  sul-  .-.,,   .  ,   .  •>       r 

pkateof  soda,  SALT. — This  is  a  white  salt,  forming  crys- 
and  itsprcpa-  ta}s  belonging  to  the  third  system,  such  as 

ration.  J 

are  represented  in  the  fig- 
ure. It  is  used  to  some  extent  in  medi- 
cine, and  in  large  quantities  for  the  pro- 
duction of  carbonate  of  soda.  It  is  prepared  by  pour- 
ing oil  of  vitriol  upon  common  salt.  A  double  decom- 
position takes  place  between  the  salt  and  the  water  of 
the  acid  ;  hydrochloric  acid  is  formed,  which  passes  off, 
and  soda,  which  remains  combined  with  the  sulphuric 


SULPHATES.  307 

acid.  It  is  to  be  understood  that  this  reaction  between 
water  and  common  salt,  takes  place  only  when  sulphuric 
acid  is  present.  The  method  of  making  the  experi- 
ment is  given  in  the  paragraph  on  the  preparation  of 
hydrochloric  acid. 

What  is  said  115.  Sulphate  of  soda  may  be  obtained 
of  its  crystals?  m  crystals,  by  evaporation.  These  crys- 
tals, like  those  of  many  other  salts,  lose  their  combined 
water,  on  exposure  to  the  air,  and  become  converted 
into  a  white  powder.  This  change  is  called  efflores- 
cence, and  the  salt  which  experiences  it  is  called  efflo- 
rescent. In  preparing  the  salt  on  a  large  scale,  for 
conversion  into  carbonate  of  soda,  large  quantities  of 
hydrochloric  or  muriatic  acid  are  incidentally  pro- 
duced. 

Whatissul-  77^'  SULPHATE  OF  BARYTA. — The  sul- 
pkate  of  ba-  phate  of  baryta  is  a  white  insoluble  sub- 

ryta?     How  .   / 

prepared?  stance,  which  may  be  obtained,  as  a  pre- 
cipitate, by  double  decomposition  of  any 
soluble  baryta  salt  with  a  soluble  sulphate.  It  is  a 
mineral  of  frequent  occurrence,  known  as  heavy  spar. 
It  is  used  for  the  adulteration  of  white  lead,  in  which 
it  may  be  easily  detected  as  a  residue,  on  dissolving 
the  white  lead  in  dilute  nitric  acid.  The  sulphate  of 
lead  is  another  of  the  few  insoluble  sulphates. 

777.   ALUM. — Ordinary  alum  is  a  double 

Describe  \ 

alum,  and  its     sulphate   of  alumina  and  potassa.      Solu- 

prcparation.        ^^    of  the  tWQ  ^^  when  mixed?  CQm_ 

bine  to  form  the  double  salt.  The  sulphate  of  alu- 
mina required  in  the  process  may  be  obtained  by  dis- 
solving alumina  from  common  clay  by  sulphuric  acid. 


308  SALTS. 

Or  it  may  be  produced  by  exposing  cer- 
tain clays  or  slates,  which  contain  sul- 
phuret  of  iron  to  the  action  of  the  air. 
Under  these  circumstances,  the  sulphur 
becomes  converted  into  sulphuric  acid, 
which  unites  with  both  oxide  of  iron  and  alumina. 
From  this  mixture  the  protosulphate  of  iron  is  sepa- 
rated by  crystallization,  leaving  a  solution  of  sulphate 
of  alumina  to  be  used  in  the  preparation  of  alum. 
What  is  burnt  ^8.  On  heating  alum  in  a  crucible  or 
alum  ?  pipe-bowl,  it  swells  up  into  a  light  porous 

mass,  and  is  converted  into  burnt  alum.  At 
the  same  time  it  loses  its  water  of  crystalliza- 
tion, of  which  it  contains  twenty-four  molecules 
to  each  molecule  of  the  double  sulphate. 

779.   OTHER  ALUMS. — The  name,  alum, 

What  is  said 

of  other  is  appplied  to  a  number  of  salts  of  analo- 

gous composition  to  the  common  alum  al- 
ready described.  In  one  of  these,  sesquioxide  of  chro- 
mium, and  in  another,  sesquioxide  of  iron,  takes  the 
place  of  the  alumina  or  sesquioxide  of  alumina.  In 
a  third  kind  of  alum,  oxide  of  ammonium  replaces  the 
potassa.  All  of  these  alums  contain  the  same  number 
of  molecules  of  water  of  crystallization.  They  have 
all  the  same  crystalline  form,  and.  if  mixed  in  solu- 
tion will  crystallize  together.  They  are,  therefore, 
isomorphous  salts.  Their  perfect  analogy  of  composi- 
tion will  be  best  seen  by  the  inspection  of  their  formu' 
Ise,  given  in  the  Appendix. 

What  is  said  780.       OTHER    SULPHATES. VlTRIOLS. 

of  vitriols?       Several  of  the  sulphates  have  received  the 


NITRATES.  309 

common  name  of  vitriols.  Sulphates  of  zinc,  copper, 
and  iron  are  called  respectively  white,  blue,  and  green 
vitriol.  Green  vitriol  readily  absorbs  oxygen  from  the 
air,  and  becomes  brown,  from  the  accumula- 
tion of  peroxide  of  iron  upon  its  surface.  A 
solution  of  it  is  changed  to  a  yellowish-red 
color,  by  the  oxidizing  action  of  either  nitric 
acid  or  chlorine.  A  crystal  of  blue  vitriol  is 
represented  in  the  figure.  The  form  belongs  to  the 
fifth  system. 

NITRATES. 

How  are  ni-          781.  The  nitrates  are  formed  by 
transformed?    fa^  action  of  nitric  acid  on  metals, 
as  already  explained,  and  also  by  the  action  of 
the  acid  on  oxides  previously  formed.     In   the 
latter  case,  the  metallic  oxide  takes  the  place  of 
the  water  of  hydration,  which  always  belongs 
to  the  acid.     They  are  also  produced  by  double 
decomposition.     The  figure  represents  a  crystal  of  salt- 
petre.    The  form  belongs  to  third  system.     This  latter 
method  is  illustrated  below,  in  the  preparation  of  nitrate 
of  potassa  from  the  nitrate  of  lime. 

782.     NITRATE  OF  LIME. — This  salt  is 

How  is  nitrate  . 

of  lime,  pro-  of  considerable  interest,  from  the  fact  that 
it  is  employed  in  the  production  of  salt- 
petre or  nitre.  It  is  formed  in  the  so  called,  nitre  beds, 
by  mixing  together  refuse  animal  matter  with  earth  and 
lime.  In  the  gradual  putrefaction  of  the  animal  mat- 
ter which  follows,  its  nitrogen  takes  oxygen  from  the 


310  SALTS. 

air,  and  is  converted  into  nitric  acid.  The  acid  then 
combines  with  the  lime  to  form  the  nitrate.  The  salt 
is  afterward  extracted  by  water.  The  formation  of 
nitric  acid,  above  mentioned,  takes  place  only  in  the  pre- 
sence of  alkaline  substances.  In  their  absence  the  ni- 
trogen passes  off,  combined  with  hydrogen,  as  am- 
monia. Even  in  the  presence  of  lime,  there  is  reason 
to  believe  that  ammonia  is  first  formed,  and  its  consti- 
tuents afterwards  converted  into  nitric  acid  and  water. 

783.  NITRATE  OF   POTASSA. — NITRE,   OR 

Explain  the 

formation  of  SALTPETRE. — This  salt  is  a  constituent  of 
certain  soils,  especially  in  warm  climates. 
These  soils  always  contain  lime,  and  are  said  to  be 
never  entirely  destitute  of  vegetable  or  animal  matter. 
It  is  obvious,  therefore,  that  nitrate  of  potassa  may  be 
formed  in  them,  as  the  same  salt  of  lime  is  formed  in 
the  nitre  beds  just  described.  A  small  proportion  of 
nitric  acid  exists  in  the  atmosphere,  combined  with  am- 
monia. This,  also,  may  be  a  source  of  part  of  the 
nitric  acid  of  the  nitrous  soils.  Again,  it  is  probable 
that  nitric  acid  is  slowly  formed  from  the  atmosphere 
by  the  direct  combination  of  its  elements  in  the  porous 
soil.  Nitre,  on  being  highly  heated,  yields  a  third  of 
its  oxygen  in  the  form  of  gas. 

784.  Nitre  is  obtained  from  nitrous  soils 

Hew  ^s  nitre 

obtained  from,    by  lixiviation  with  water,  and  subsequent 

nitron  soils?     crystallizatioiL         From      nitrate     of     Iim6j 

it  is  produced  by  double  decomposition  with  carbonate 
of  potassa.  Carbonate  of  lime  precipitates,  while  nitrate 
of  lime  remains  in  solution.  This  may  be  afterward 
poured  off,  evaporated,  and  crystallized. 


NITRATES.  311 

785.    USES  OF  NITRE.  —  Nitre  is   exten- 

Mention  some 

of  the  uses  sively  employed  by  the  chemist  and  in  the 
arts,  as  an  oxidizing  agent.  A  few  grains 
of  it  introduced  into  a  solution  of  green  vitriol,  or  sul- 
phate of  iron,  to  which  some  free  sulphuric  acid  has 
been  added,  will  immediately  change  its  color.  The 
sulphuric  acid  sets  nitric  acid  at  liberty,  to  which  the 
oxidation  and  change  of  color  are  to  be  attributed. 
Nitre,  when  heated,  yields  part  of  its  oxygen,  as  before 
stated.  If  heated  with  metals,  it  converts  them  into 
oxides.  The  principal  use  of  nitre,  is  in  the  manufac- 
ture of  gun-powder. 


Howareni-  -    NlTRATE    OF    AMMONIA.  -  LAUGHING 

trate  of  am-      GAS.  —  Nitrate  of  ammonia  may  be  prepared 

monia  and  ,, 

laughing  gas     irom    the   carbonate,  by  evaporation  with 
produced?         nitric  acid      When  heatedj  the  hydrogen 

of  the  ammonia,  and  an  equivalent  quantity  of  the  ox- 
ygen of  the  nitric  acid,  unite  to  form  water,  and  the 
residue  of  both  passes  off  as  protoxide  of  nitrogen,  or 
nitrous  oxide.  The  compound  is  also  called  laughing 
gas,  from  the  exhilarating  effects  which  it  occasions, 
when  breathed  in  considerable  quantity.  Impurity 
of  material  or  excess  of  heat  occasion  the  production 
of  an  impure  and  deleterious  gas.  In  view  of  these 
facts,  the  preparation,  and  inhalation  of  laughing  gas 
is  not  to  be  recommended  to  the  student. 
Ex  lain  the  ^^  '  GUN-POWDER.  —  Gun-powder  is  a 

action  of  the  mixture  of  nitre,  charcoal,  and  sulphur. 
°o/  When  ignited,  the  carbon  burns  instanta- 
neOusly,  by  help  of  the  oxygen  of  the  nitre, 
thus  producing  a  large  volume  of  carbonic  acid  gas.  To 


312  SALTS. 

this  gas,  together  with  the  nitrogen  which  is  also  set  at 
liberty  at  the  same  moment,  the  force  of  the  explosion 
is  due.  The  sulphur,  at  the  same  time,  combines  with 
the  potassium  of  the  nitre,  and  remains  with  it  as  a 
sulphuret  of  potassium.  Three  equivalents  of  carbon 
to  one  of  nitre,  and  one  of  sulphur,  expresses  very 
nearly  the  composition  of  gun-powder.  It  varies,  how- 
ever, according  to  the  uses  for  which  it  is  intended, 
and  the  country  in  which  it  is  manufactured.  From 
the  proportion,  by  equivalents,  the  relative  weight  of 
the  constituents  can  readily  be  calculated. 

788.  COLLECTION  OF   THE   GASES. — For 

How  arc  the  .  -in-  /• 

gases  col-          the  production  and  collection  of  the  gases 
evolved  in  the  combustion  of  gun-powder, 
the  fuses  of  ordinary  "firecrack- 
ers" may  be  employed.     Several 
of  them  are  to  be  ignited  at  the 
same  time,  in  an   ordinary  test- 
tube.     The  mouth  of  the  latter 
being  then  brought  under  a  filled 
and  inverted  vial,  the  gases  are 
collected  as  fast  as  they  are  evolved. 

789.  NITRATE  OF  SILVER. — Nitrate    of 

Describe  ni-  .,  .  i          j     • 

trate  of  silver,  silver,  or  Lunar  caustic,  is  employed,  in 
What  are  its  surgerVj  for  cauterizing  wounds.  A  solu- 
tion of  the  salt  in  which  the  oxide  has 
been  precipitated  by  ammonia,  and  re-dissolved  by  a 
slight  excess,  is  extensively  employed  as  an  indelible 
ink.  The  black  color  comes  from  oxide  of  silver,  and 
finely  divided  metal,  precipitated  in  the  cloth.  It 
may  be  removed  by  soaking  in  solution  of  common 


CARBONATES.  313 

salt,  and  thus  converting  the  silver  of  the  mark  into 
chloride  of  silver.  This  is  soluble  in  ammonia,  and 
may  be  afterward  extracted  by  that  agent.  Nitrate 
of  silver  is  also  the  basis  of  most  dyes  for  the  hair. 
Describe  the  790.  OTHER  NITRATES. — Nitrate  of  soda 
other  nitrates.  js  a  wnite  salt,  found  native  in  South 
America.  It  is  used  in  the  manufacture  of  nitric  acid, 
and,  to  some  extent,  as  a  fertilizer  of  the  soil.  The 
remaining  nitrates  are  soluble  salts,  of  colors  corres- 
ponding to  the  solutions  of  the  metals,  as  already  de- 
scribed. The  uses  of  the  nitrates  of  silver  and  bismuth 
have  already  been  mentioned. 

CARBONATES. 

Describe  the          791.  CARBONATES. — The  carbonates  are, 
carbonates.        for  tne  most   part)  wnite   or   light  colored 

salts,  of  which  chalk  may  serve  as  an  example.  The 
carbonate  of  copper  is  found  native,  both  as  blue  and 
green  malachite.  All  of  the  carbonates, 
excepting  those  of  the  alkalies,  may  be 
decomposed  by  heat.  The  latter  are  sol- 
uble, and  retain  their  acid  at  the  highest  temperatures. 
The  figure  represents  a  crystal  of  carbonate  of  lime  or 
calc  spar. 

792.  PREPARATION. — The  insoluble  car- 

How  are  the  ... 

insoluble  car-  boiiates  may  be  produced  by  precipitating 
solutions  of  the  metals  or  their  salts,  by 
carbonic  acid  or  solutions  of  the  alkaline 
carbonates.  In  the  latter  case,  a  double  decomposition 
occurs,  with  exchange  of  acids  and  bases. 

14* 


314 


SALTS. 


What  is  said 
of  carbonate 
of  potassa  ? 


Describe  car- 
bonate of 
soda. 


793.  CARBONATE  OF  POTASSA. — POTASH. 
The  method  of  preparing  potash  and 
pearlash,  from  wood  ashes,  has  already 
been  considered  in  the  paragraph  on  Potassa.  Saleratus 
is  a  carbonate  containing  a  large  proportion  of  carbonic 
acid.  Its  use,  for  u  raising"  bread  and  cake,  is  familiar. 
The  acid  employed  with  it,  sets  the  carbonic  acid  gas 
at  liberty  and  thus  puffs  up  the  "  sponge." 

794.  CARBONATE  or  SODA. — SODA. — 
Carbonate  of  soda  is  commonly  known 
under  the  name  of  soda.  It  is  a  white 
soluble  salt,  familiar  from  its  use  in  Seidlitz  and  soda 
powders.  Its  carbonic  acid  is  the  source  of  the  effer- 
vescence in  these  preparations. 

795.  Carbonate  of  soda  is  prepared  from 

flow  i.s  carbo-  .  . 

note  of  soda  the  sulphate  of  soda.  1  his  salt  being 
prepared?  heated  with  charcoal  is  converted  into 
sulphide  of  sodium.  On  heating  the  latter  with  car- 
bonate of  lime,  a  double  de- 
composition occurs,  and  car- 
bonate of  soda  is  produced, 
with  sulphide  of  calcium  as 
an  incidental  product.  Both 
parts  of  the  process  are  com- 
bined in  practice.  Sulphate 
of  soda,  chalk,  and  coal,  are  heated  together  in  a  rever- 
beratory  furnace,  the  carbonate  of  soda  is  then  dissolved 
out  from  the  fused  mass,  dried,  purified,  and  subse- 
quently crystallized.  The  sulphide  of  calcium  would 
dissolve  at  the  same  time,  and  thus  defeat  the  process, 
were  it  not  rendered  insoluble  by  combination  with  a 
certain  quantity  of  lime. 


CARBONATES.  315 

Describe  an-  796.  Another  method  of  manufacturing 
other  method,  carbonate  of  soda,  consists,  essentially, 
in  separating  sulphur  from  the  sulphate,  by  means  of 
oxide  of  iron,  and  substituting  carbon  in  its  place.  In 
this  process  also,  the  materials  are  heated  with  charcoal, 
in  a  reverberatory  furnace,  and  the  carbonate  afterward 
extracted  by  water.  The  impure  uncrystallized  carbo- 
nate of  soda,  is  known  in  commerce,  as  soda  ash,  and 
is  largely  employed  in  the  manufacture  of  hard  soap, 
and  in  other  processes. 

What  is  sal  797.  CARBONATE  OF  AMMONIA. SAL  VOL- 

volatile?  ATILE. — The  ordinary  sal  volatile  of  the 

shops,  used  as  smelling  salts,  is  a  carbonate  containing 
three  equivalents  of  acid  to  two  of  base.  It  wastes  away 
gradually  in  the  air,  and  passes  off  in  a  gaseous  form. 

798.  PREPARATION. — Sal  volatile  is  pre- 

How  is  sal  . 

volatile  pre-  pared  by  heating  together  carbonate  of 
pared  \ime  and  chloride  of  ammonium.  Carbo- 

nate of  ammonia  immediately  passes  off',  while  chloride 
of  calcium  remains  behind.  The  carbonate  is  led  into 
a  cold  pipe  or  chamber,  where  it  takes  the  solid  form. 
The  mixture  of  chalk  and  sal  ammoniac  is  sometimes 
used  as  smelling  salts.  The  production  of  sal  volatile 
from  the  mixture  is  very  gradual  if  heat  is  not  applied. 

799.  The  property  from  which 

How  is  it 

proved  to  be  the  salt  receives  its  name,  may 
volatile  f  be  illustratedj  by  holding  in  its 
vicinity  a  rod  or  roll  of  paper,  moistened  with 
strong  muriatic  acid.  A  dense  cloud  of  sal 
ammoniac  is  immediately  produced  in  the 
air,  from  the  union  of  the  two  vapors.  The 


316 


SALTS. 


experiment  is  more  striking,  if  the  sal  volatile  is  warmed 
in  a  cup  or  other  vessel.  This  salt  is  sometimes 
used  by  bakers  for  making  bread  and  cakes  light  and 
spongy. 

800.  CARBONATE  OF  LIME. — Carbonate 
of  carbonate     of  lime,  in  the  form  of  chalk,  marble,  arid 
of  ime?          ordinary   limestone,  is  a   most    abundant 
mineral.     Whole  mountain  chains  consist  of  the  latter 
rock.     The  shells  of  shell-fish  are  principally  carbon- 
ate of  lime.     There  is  good  reason,  indeed,  to  believe 
that  all  limestones  have  their  origin  in  accumulations 
of  such  shells,  which  have  been  consolidated  in  the 
course  of  ages. 

801.  SOLUBILITY  IN  CARBONIC  ACID.— 
The    solubility    of  carbonate    of  lime  in 
carbonic  acid  is  readily  shown,  by  passing 
a  current  of  the  gas  through 

water  clouded  with  pulver- 
ized chalk  or  marble.  Other  mineral 
substances  which  form  the  food  of  plants 
are  dissolved  by  the  same  means,  and 
then  find  their  way  into  the  roots,  to  5 
subserve  the  purposes  of  vegetable  life. 

802.  INCRUSTATIONS  IN  BOILERS. — Car- 

What  is  said 

of  incrusta-  bonate  of  lime  dissolved  in  carbonated 
twns  m  boil-  water  js  again  precipitated  on  boiling  the 
solution.  This  is  owing  to  the  escape  of 
the  acid.  Incrustations  in  tea-kettles  and  steam-boilers, 
in  limestone  districts,  owe  their  origin  to  the  same  cause. 
In  some  cases,  the  crust  is  formed  of  gypsum,  or  other 
earthy  matters  contained  in  the  water.  One  method 
of  avoiding  this  inconvenience  in  steam-boilers,  is  by 


How  is  the 
solubility  of 
carbonate  of 
lime  in  car- 
bonic acid 
shown  ? 


PHOSPHATES.  3l7 

the  addition  of  a  smaller  boiler,  in  which  the  water  is 
first  heated,  arid  its  sediment  deposited. 
Give  the  sta-          803.  STALACTITES. — The  masses  of  car- 
lactites.  bonate  of  lime   which  hang  like  mineral 

icicles  from  the  roofs  of  caverns  are  called  stalactites. 
The  water  that  penetrates  the  soil  is  the  architect  of 
these  curious  forms.  Impregnated  with  carbonic  acid, 
derived  from  decaying  vegetation,  it  takes  up  its  load 
of  carbonate  of  lime  as  it  settles  through  the  rock,  and 
deposits  it  again  on  exposure  to  the  air  of  the  cavern, 
in  various  and  often  fantastic  shapes.  Another  portion 
of  water,  dripping  to  the  floor  of  trje  cavern,  builds  up 
similar  forms,  called  stalagmites,  from  below. 

804.  ARTIFICIAL  MARBLE. — The  surface 

How  ts  artifi- 

rial  marble  of  wood  or  stone  may  be  marbled  by  cov- 
produccd?  ering  it  with  successive  coats  milk  of  lime, 
and  allowing  each  in  turn  to  dry  before  the  next  is  ap- 
plied. The  surface  is  then  smoothed  and  polished,  and 
carbonic  acid  finally  applied,  by  which  it  is  converted 
into  marble.  The  milk  of  lime  is  simply  a  mixture 
of  slaked  lime  and  water,  and  may  be  so  colored  as  to 
produce  a  variegated  surface. 

PHOSPHATES 
Describe  the  805.      PHOSPHATES. The      phosphates, 

phosphates.  wjth  the  exception  of  those  of  the  alka- 
lies, are,  for  the  most  part,  white  insoluble  salts. 
Phosphate  of  lime  may  be  taken  as  an  ex- 
ample. The  white  residue  which  is  obtained 
on  heating  the  bones  of  animals,  until  all  the 
animal  matter  is  destroyed  and  expelled,  is  principally 
phosphate  of  lime. 


318  SALTS. 

806.  Ordinary   phosphoric  acid    has  the 

Why  is  ordi-  ,,  ,  .    . 

naryphospho-    property  of  combining  with   and  neutrah- 

edtrTba  ticT~  zing  tnree  e(luivalents  °f  Dasej  instead  of 
one,  as  is  the  case  with  most  other  acids. 
It  is  therefore  called  a  tribasic  acid.  The  hyd  rated 
acid  contains,  also,  three  equivalents  of  water,  and  may 
be  regarded  as  a  salt  in  which  the  water  acts  the  part 
of  base.  Arsenic  acid  is  similar  in  this  respect,  as  well 
as  in  the  amount  of  oxygen  which  it  contains,  and  in 
the  salts  which  it  forms  with  bases.  Two  other  kinds 
of  phosphoric  acid  may  be  prepared  from  that  above 
mentioned  ;  the  first  combines  with  one,  and  the  second 
with  two  equivalents  of  base. 

807.  PREPARATION.  —  The  phosphates  of 

How  are  the  .  f         J 

phosphates  the  alkalies  may  be  produced  by  the  ac- 
preparcd?  tion  of  phosphoric  acid  on  the  proper  car- 
bonates. The  remaining  phosphates  may  be  precipi- 
tated by  solution  of  phosphate  of  soda,  from  solutions 
of  the  metals  or  their  salts.  As  in  other  cases  of  pre- 
cipitation, there  is  here  a  double  decomposition,  with 
exchange  of  acids  and  bases. 

808.     SUPERPHOSPHATE    OF    LIME.  —  A 

Describe  the  .  •»•-»• 

preparation      mixture  bearing  this  name,  formed  by  the 


action  of  dilute  sulphuric  acid  on  burned 
bones,  is  extensively  used  as  a  fertilizer  of 
the  soil.  The  sulphuric  acid,  when  added,  appropri- 
ates part  of  the  lime  of  the  bones,  forming  with  it 
gypsum  ;  at  the  same  time,  it  leaves  the  phosphoric 
acid  which  it  displaces,  free  to  combine  with  another 
portion  of  phosphate  of  lime  and  thereby  to  render  it 
soluble.  The  commercial  article  is  a  mixture  of  this 


SILICATES.  319 

soluble  substance  with  the  gypsum  and  animal  char- 
coal produced  in  its  formation.  Other  materials  are 
often  added,  increasing  or  diminishing,  according  to 
their  nature,  its  agricultural  value.  The  basis  of  the 
manufacture,  is  commonly  the  refuse  bone  black  of 
the  sugar  refineries  employed  in  the  process. 

809.   OTHER  PHOSPHATES. — The   phos- 

Whatis  mid  . 

of  other  phos-  phate  of  soda  is  used  in  medicine 
phates?  and  j^  tne  cnemistj  to  produce 

other  phosphates.  The  phosphate  of  silver  is 
a  beautiful  yellow  precipitate,  obtained  by  pre- 
cipitating salts  of  silver  with  phosphate  of 
soda  or  any  other  salt  containing  phosphoric  acid. 

SILICATES 

What  is  said  810.  The  silicates  form  an  exceedingly 
of  silicates?  iarge  c|ass  of  salts.  They  are,  for  the 
most  part,  insoluble,  and  are  variously  colored. 
Mica  and  feldspar,  two  of  the  constituents 
of  granite,  may  serve  as  examples.  As  com- 
ponents of  this  and  other  rocks,  the  silicates 
make  up  a  very  considerable  portion  of  the 
mass  of  the  earth. 

811.  PREPARATION. — Most  silicates  may 

How  are  sili-  .  f  _ 

catespre-  be  artificially  formed  by  fusing  together 
pared?  quartz  sand,  with  the  proper  oxide.  This 

is  done  in  the  manufacture  of  glass,  to  be  hereafter 
described.  Silicates  may  also  be  formed  by  precipita- 
ting solutions  of  metals  or  their  salts  by  the  solution 
of  an  alkaline  silicate. 


320  SALTS. 

.812.  CLAY. — Clay  is  a  silicate  of  alu- 
composition  mina,  commonly  containing  silicate  of  po- 
tassa  and  other  materials  in  small  pro- 
portion. The  best  kaolin  or  porcelain  clay  is  perfectly 
white,  and  is  nearly  pure  silicate  of  alumina. 
How  is  soluble  813.  SOLUBLE  GLASS.— Soluble  glass  is 
glass  made?  made  by  fusing  sand  with  potassa  or  soda. 
Its  production  may  be  illustrated  in  a  soda  bead,  by 
subsequently  re-fusing  it,  with  addition  of  sand.  As 
the  silicic  acid  combines  with  the  soda,  carbonic 
acid  is  expelled,  as  will  be  evident  from  an  efferves- 
cence on  the  surface  of  the  bead.  Soluble  glass  is 
sometimes  used  as  a  sort  of  varnish  for  rendering  wood 
fire  proof. 

814.  WINDOW  GLASS. — Common  window 
•manufacture     glass  is  a  silicate  of  lime   and  soda.     To 

°flaWssnd°W  f°rm    il>  Chalk>  S°da>  quartz   salld    and    °ld 

glass  are  fused  together  until  the  mass  be- 
comes fluid.  The  molten  glass  is  then  blown,  by 
means  of  an  iron  tube,  as  soap  bubbles  are  blown 
with  a  pipe.  The  first  form  of  the  bubble  is 
that  represented  in  the  figure.  The  glass  blower 
next  contrives  to  lengthen  out  the  bubble,  as  he 
blows  it,  to  a  larger  size,  and  finally  to  blow  out 
the  end  by  a  strong  blast  from  his  lungs.  It 
is  then  trimmed  with  a  pair  of  shears,  and  the 
other  end  cracked  off  by  winding  round  it  a  thread 
of  red  hot  glass.  Such  a  thread  is  readily  produced 
by  cfipping  an  iron  rod  into  the  pot  of  molten  glass,  and 
then  withdrawing  it.  The  bubble  of  glass  is  thus 


GLASS. 


321 


brought  to  the  form  of  a  cylinder,  such  as  is 
represented  in  the  figure.  The  cylinder  is 
then  cracked  longitudinally,  by  letting  a  drop 
of  water  run  down  its  length,  and  following  it 
by  a  hot  iron.  It  is  subsequently  reheated, 
opened,  and  flattened  out  into  a  sheet,  which 
is  then  cut  into  paries  of  smaller  size,  if  required. 
How  are  glass  815.  GLASS  TUBES.— To  make  a  glass 
tubes  made?  tube,  a  bulb  is  first  blown,  such  as  is  repre- 
sented on  the  previous  page.  An  assistant  then  at- 
taches his  tube  to  the  hot  bulb  at  the  opposite  side, 
and  moves  backward.  The  glass  is  thus  drawn  out, 
as  if  it  were  wax,  and  the  cavity  within  it  is  elongated 
to  a  smooth  and  perfect  bore. 

816.     GLASS  BOTTLES  — Bottles    and  a 

Glass  bottles?  .  f  . 

great  variety  of  other  objects  of  glass,  are 
made  by  the  enlargement  of  similar  bulbs  within  a 
mould  of  the  required  shape.  Bottle  glass  is  usually 
made  of  cheaper  and  less  pure  materials  than  window 
glass,  and  contains,  in  addition  to  the  materials  before 
mentioned,  alumina  and  oxides  of  iron  and  manganese. 
It  owes  its  green  color  to  the  protoxide  of  iron. 
Glass  mir-  817.  GLASS  MIRRORS. — Plate  glass,  such 

rors?  as   is    used  for  mirrors,   instead   of  being 

blown,  is  cast  in  metallic  tables  of  the  required  shape, 
and  then  rolled  out  and  polished. 
Wha.n*crys~  818.  CRYSTAL  GLASS. — This  name  is 
tal  glass  ?  given  to  a  highly  brilliant  glass,  contain- 
ing potassa  and  litharge  as  bases.  It  is  used  for  prisms, 
lenses,  lustres,  and  the  finer  qualities  of  cut  glass  ware. 

14* 


SALTS. 


With  the  addition  of  borax,  it  is  also  employed  for  im- 
itations of  precious  stones. 

What  is  ena-  819.  ENAMEL. — Enamel  is  an  opaque 
md?  glass,  produced  by  the  addition  of  some 

material  which  does  not  dissolve  in  the  fused  mass. 
Binoxide  of  tin  is  the  material  commonly  employed. 
Various  tints  may  be  imparted  to  enamel,  as  to  ordi- 
nary glass,  by  the  addition  of  small  quantities  of  me- 
tallic oxides.  A  thin  surface  of  enamel  is  often  baked 
on  to  a  metallic  surface,  as  in  the  case  of  watch  dials, 
and  various  objects  of  jewelry. 

How  is  glass  820.  COLORED  GLASS. — Glass  is  colored 
colored?  an(j  stained  by  the  addition  of  various  me- 

tallic oxides.  The  peculiar  coloring  effects  of  these 
substances  have  already  been  mentioned,  in  the  sec- 
tion on  Oxides. 

EARTHENWARE. 

What  is  the  821.  Clay  is  the  basis  of  all  earthenware, 

basis  of  all       from  the  finest  porcelain  to  the  coarsest 

earthenware? 

How  is  porce-     brick.     Being  first  fashioned  by  moulds  or 

lain  made?          ^_  means  jnto  the 


proper  form,  it  is  dried,  baked,  and 
subsequently  glazed,  to  render  it 
impervious  to  water.  In  the  man- 
ufacture of  porcelain,  glazing  is  not 
essential.  Sand  and  chalk  are  ad- 
ded to  the  original  material,  and 
the  heat  is  carried  so  high  as  to 
bring  the  whole  mass  into  a  semi- 
vitreous  condition.  This  is  also 
the  case  in  certain  kinds  of  stone- 


BORATES.  323 

ware.  Porcelain  is,  however,  commonly  glazed  to  add 
to  its  beauty. 

822.   GLAZING. — Earthenware    after  its 

Describe  tlie 

process  of  first  baking  is  porous,  and  therefore  unfit 
glazing.  ^  mogt  useg  ^or  Wj1'cj1  ^  js  intended.  It 

is  subsequently  covered  with  a  thin  paste  formed  of 
the  constituents  of  glass.  Being  then  subjcted  a 
second  time  to  the  heat  of  the  furnace,  a  thin  glass 
or  glaze  is  formed  upon  the  surface.  The  glazing 
of  certain  wares  is  effected  by  exposure  at  a  high 
temperature  to  vapors  of  common  salt.  A  double  de- 
composition ensues  with  the  oxide  of  iron  which  the 
ware  contains,  by  which  soda  is  formed.  This  imme- 
diately fuses  with  the  silica  and  other  materials  to  form 
the  glaze.  The  chloride  of  iron  which  is  formed  at 
the  same  time  passes  off  as  vapor.  A  paste  of  pounded 
feldspar  and  quartz,  to  which  borax  is  sometimes  added, 
is  employed  in  glazing  porcelain. 

823.  PORCELAIN  PAINTING. — Metallic 
of 'porcdTin  oxides  form  the  basis  of  the  pigments  used 
painting?  «n  pajntmg  upon  porcelain.  The  color- 
ing effect  of  the  different  pigments  is  mentioned  in  the 
chapter  on  metallic  oxides.  The  patterns  on  ordinary 
.earthenware  are  first  printed  on  paper,  and  then  trans- 
ferred, by  pressure,  to  the  unglazed  ware.  The  paper 
is  afterwards  removed  by  a  wet  sponge. 


BORATES. 

What  is  824.  BORAX. — Borax  is  the  only  impor- 

lorax?  tant  salt  among  the  compounds  of  boracic 


324  SALTS. 

acid.  The  salt  contains  two  atoms  of  acid  to 
one  of  base,  and  is  therefore  a  biborate.  It  is  a 
white  soluble  salt,  which  swells  up  when  heat- 
ed, in  consequence  of  the  escape  of  its  water 
of  crystallization. 

How  is  borax  825.  PREPARATION. — Borax  is  found  in 
prepared?  solution  in  the  water  of  certain  shallow 
lakes  in  India.  It  remains  as  an  incrustation  in  the 
beds  of  these  lakes  when  they  dry  up  in  summer.  It 
is  also  prepared  by  the  action  of  a  solution  of  boracic 
acid  on  carbonate  of  soda. 

What  is  said  826.  BORAX  GLASS. — The  light  spongy 
of  borax  glass?  mass  which  is  produced  on  heating  borax, 
may  be  melted  down  by  greater  heat  and  converted  into 
borax  glass.  This  glass  has  the  property  of  dissolving 
metallic  oxides,  and  receiving  from  them  peculiar  colors, 
as  described  in  a  former  paragraph.  The  chemist  often 
determines  the  metal  which  a  salt  or  oxide  contains, 
by  the  color  which  it  thus  imparts  to  glass.  The 
method  of  making  the  experiment  has  already  been 
given. 

827.  SOLDERING,  WELDING,  ETC. — Borax 

Why  is  borax      .  .  \      . 

employed  in  is  employed  in  soldering  metals,  to  keep 
soldering?  ^  metallic  surfaces  clean.  It  does  this 

by  dissolving  the  coating  of  oxide  which  forms  upon 
them,  and  forming  with  it  a  glass  which  is  fluid  at  a 
high  temperature,  and  easily  pushed  aside  by  the 
melted  solder.  Its  use  in  welding  iron  depends  on  the 
same  property.  Borax  is  employed,  to  some  extent,  in 
medicine.  It  is  also  a  constituent  of  the  glass  called 


CHROMATES.  325 

jewellers  paste,  which  is  used  in  producing  imitations 
of  precious  stones. 


CHROMATES. 
828.  CHROME  YELLOW. — To  prepare  this 

How  is  chrome        .  .,  .    , 

yellow  pre-        pigment,    a   solution  of    the    commercial 
pared?  bichromate  of  potassa  is  added  to  a  solution 

of  sugar  of  lead.  A  double  decomposition  ensues ;  the 
result  of  which  is  the  production  of  a  beautiful 
yellow  precipitate,  known  as  chrome  yellow. 
The  precipitate  is  a  chromate  of  lead.  The 
bichromate  of  potassa  used  in  the  experiment,  is 
made  from  the  mineral  chrome  iron,  which  has 
been  mentioned  in  a  previous  chapter.  The  acid  itself, 
which  is  without  practical  applications,  may  be  made 
from  the  salt.  It  contains,  like  sulphuric  acid,  three 
atoms  of  oxygen. 

How  is  chrome  ^^'   CHROME    ORANGE. — Chrome  yellow 

yellow  con-        may  be  converted  into  chrome  orange,  by 

verted  into  .  .  ,  ,  . 

chrome  digestion  with  carbonate  of  potassa.    Cloth 

dyed  yellow  by  dipping  it  alternately  into 
a  solution  of  bichromate  of  potassa  and  sugar  of  lead,  is 
instantaneously  changed  to  orange  by  immersion  in 
boiling  milk  of  lime.  This  action  of  the  lime,  as  well 
as  that  of  carbonate  of  potassa,  depends  upon  its  ab- 
stracting a. certain  portion  of  the  chromic  acid,  leav- 
ing thereby  a  chromate  of  lead  of  different  composi- 
tion and  color. 


326  SALTS. 

830.  CHROME    GREEN.  —  On  adding   sul- 

Dcscribe  the  .          .  ° 

preparation       phuric  acid  and  a  few  drops  of  alcohol  to  a 


solution  of  bichromate  of  potassa,  the  solu- 
tion is  immediately  changed  from  red  to 
green.  The  alcohol  has  taken  oxygen  from  the  chro- 
mic acid,  and  converted  it  into  oxide,  which  remains 
in  solution,  as  a  soluble  sulphate.  Part  of  the  sulphu- 
ric acid  has  at  the  same  time  combined  with  the  potassa, 
to  form  sulphate  of  potassa.  It  is  to  the  presence  of 
the  sulphate  of  chromium  in  solution  that  the  color  of 
the  liquid  is  due.  By  adding  an  alkali  to  the  solution, 
a  green  precipitate  of  the  hydrated  oxide  is  produced. 
This  oxide  forms  a  kind  of  "  chrome  green."  App.  830. 

MAKGANATES. 

831.  CHAMELEON  MINERAL.  —  By   fusion 

What  is  cha-  ...  , 

meleon  miner-  with  nitre,  the  black  oxide  of  manganese 
may  be  still  further  oxidized,  and  converted 
into  an  acid.  The  new  acid  at  the  same  time  com- 
bines with  the  potassa  of  the  nitre  to  form  manga  nate 
of  potassa.  This  salt  has  been  called  chameleon  min- 
eral, from  the  spontaneous  change  of  color  which 
takes  place  in  its  solutions. 

832.  PREPARATION.  —  The    experiment 

How  is  chame- 

leon  mineral  may  be  made  by  filling  a  pipe  stem  with 
prepare  .  a  mjxture  of  tne  materials,  and  thrusting  it 
into  burning  coals.  It  may  be  made  on  a  still  smaller 
scale  before  the  blow-pipe,  using  a  broken  pipe-bowl  to 
support  the  materials.  The  compound  dissolves  in 
water,  forming  a  green  solution,  which  on  standing 
is  gradually  changed  to  a  beautiful  red. 


THE    DAGUERREOTYPE.  327 

833.   EXPLANATION.  —  The  addition  of  a 

Explain  the 

action  of  sul-  few  drops  of  sulphuric  acid,  produces  the 
above-mentioned  change  instantaneously. 
This  acid  combines  with  the  potassa, 
setting  the  manganic  acid  at  liberty.  One  portion  of 
manganic  acid  then  appropriates  part  of  the  oxygen  of 
the  other  part,  and  converts  itself  into  hypermanganic 
acid,  which  still  remains  combined  with  potassa,  im- 
parting the  red  color  to  the  solution.  The  deoxydized 
portion  of  the  acid  precipitates,  at  the  same  time,  as  bin- 
per  oxide.  The  remaining  manganates  are  not  of  especial 
interest  or  importance. 

THE  DAGUERREOTYPE. 
834.    THE  DAGUERREOTYPE.  —  The  da- 

Explain  the 

guerreotype  may  be  regarded  as  a  painting 


in  mercury,  upon  a  silver  surface.  The 
employment  of  mercury  is  preceded  by  what  may  be 
called  an  invisible  painting  upon  the  silver.  This  is  ac- 
complished, like  the  production  of  an  image  in  a  mirror, 
by  mere  presentation  of  the  picture,  or  other  object 
to  be  copied,  before  the  prepared  plate.  The  mercury, 
afterward  used  in  the  form  of  vapor,  adheres  to  the 
plate,  and  forms  its  white  amalgam,  just  in  proportion 
to  the  lights  and  shades  of  the  previous  image  thrown 
upon  the  plate. 

Describe  the  835.     THE    DAGUERREOTYPE    PROCESS.—  - 

process  of  ta-    jn  or(jer  to  prepare  the  plate  for  what  has 

King  daguer- 

reotypes.  above  been  called  the  invisible  painting,  it 

is  exposed  to  vapors  of  iodine,   and  thereby  covered 


328  SALTS. 

with  a  coating  of  iodide  of  silver.*  A  picture  or  face 
to  be  copied  being  presented  before  the  prepared  plate, 
the  light  which  proceeds  from  it  acts  chemically 
upon  the  iodide  of  silver.  It  decomposes  it,  to  a 
certain  extent,  and  separates  the  iodine,  thus  open- 
ing the  way  for  the  mercurial  vapor,  which  is  afterward 
to  be  employed.  The  light  has  this  effect,  just  in  pro- 
portion to  its  intensity.  That  which  proceeds  from  the 
lighter  portions  of  the  face,  or  dress,  has  most  effect  ; 
that  from  the  black  portions,  none  at  all,  and  that  from 
the  intermediate  shades,  an  effect  in  exact  proportion 
to  their  brightness.  When  the  plate  is  afterward  ex- 
posed to  the  action  of  the  mercurial  vapors,  they  find 
their  way  to  the  silver  surface  and  paint  it  white,  just 
in  proportion  as  this  chemical  effect  upon  the  iodine 
has  been  produced,  and  the  way  has  been  opened  for 
their  admission.  The  darker  portions  of  the  plate  are 
pure  silver.  They  appear  dark  in  contrast  with  the 
white  amalgam.! 

836.  USE  OF  THE  LENS. — In  taking  da- 

What  is  the 

object  of  the      guerreotypes,  a  lens  is  placed  between  the 
object  to  be  copied  and  the  plate,  in  order 
that  the  light  which  proceeds  from  the  former  may  be 
concentrated,  and  its  effect  thus  increased. 


*  Bromide  and  chloride  of  iodine,  are  employed  to  give  additional 
sensitiveness  to  the  plate.  The  iodide  is  thus  made  to  contain  a  por- 
tion of  bromide  and  chloride  of  silver. 

f  The  art  of  taking  portraits  from  the  life  by  the  Daguerreotpe  pro- 
cess, was  invented  by  Dr.  J.  W.  Draper,  of  the  University  of  New 
York. 


PHOTOGRAPHS.  329 

837.  CHEMICAL  ACTION  OF  LIGHT.  —  The 

What  is  said  .  .  .  . 

of  theckemi-     chemical   action   or  light,   on    which   the 
t    production  of  daguerreotypes  depends,  is 


rays  possess       one  of  tne  mOst  interesting  and  remarkable 

this  power  ? 

of  chemical  phenomena.  The  rays  of 
the  sun  are  so  subtle,  that  they  pass  through  solid  crys- 
tal and  leave  no  trace  of  their  passage.  Yet  with  them 
comes  a  power  that  can  overcome  the  strongest  chemical 
affinities,  and  resolve  the  compounds  which  it  has  pro- 
duced into  their  original  elements.  This  power  resides 
in  what  are  called  the  chemical,  act  wic,  or  tit/ionic  rays. 
These  are  mingled,  under  ordinary  circumstances,  with 
those  of  light,  but  are  capable  of  separation  by  certain 
media. 

What  are  pho-  $38.    PHOTOGRAPHS.  -  Pictures  produced 

tographs  ?  through  the  agency  of  light,  whether  upon 
silver,  or  paper,  are,  properly,  photographs,  or  light  pic- 
tares  ;  the  name,  however,  is  especially  appropriated 
to  the  latter.  For  the  purpose  of  illustration,  a  method 
of  producing  negative  pictures,  as  they  are  called,  will 
be  here  given. 

H™  is  scnsi-  839-    The  sensitive   paper  required  in 

tive  paper  the  process,  is  prepared  by  floating  a  slip  of 
letter-paper,  for  two  or  three  minutes,  upon 
salt  water  ;  and  then  for  double  the  time,  with  the  same 
side  down,  on  a  solution  of  nitrate  of  silver.  Chlo- 
ride of  silver  forms  within  the  fibres,  and  renders  the 
paper  sensitive  to  light.  After  each  immersion,  the  slip 
should  be  dried  off  by  blotting  paper.  When  finished,  it 
should  be  immediately  laid  away  between  the  leaves 
of  a  book,  for  protection  against  the  light. 


330  SALTS. 

840.    Such  paper,    if  placed   in    direct 

What  effect 

has  direct  sun-  sun  light,  becomes  violet,  and  then  dark 
ls?n*itive°pa-  brown,  in  the  course  of  a  few  minutes. 
per?  The  change  is  owing  to  the  partial  decom- 

position of  the  chloride  of  silver.  A  new  substance, 
of  darker  color,  is  then  produced ;  whether  a  lower 
chloride  of  different  shade,  or  a  mixture  of  metal  and 
chloride,  or  a  compound  of  oxide  and  chloride,  is  not 
very  certainly  known. 

841.    If  a  cross    or  other  device  cut 

How  may  cop- 

be  pro-  irom  dark  paper,  be  pressed  down  upon 
of  sen-  sensitive  paper,  by  means  of  a  glass  plate, 
sitive  paper  ?  and  be  left  to  cover  it  during  the  exposure 
to  light,  the  paper  will  be  pro- 
tected beneath  it,  and  an  exact 
copy  of  the  device  thus  ob- 
tained. The  most  delicate  lace 
may  be  copied  hy  the  same  method.  In  reproducing 
engravings  by  this  means,  they  must  be  previously 
rendered  translucent,  so  that  the  imprinted  portions  will 
allow  the  light  to  pass.  This  may  he  accomplished  by 
waxing  them,  with  the  help  of  a  hot  iron,  or  by  simple 
oiling.  The  dark  parts  of  the  engraving  appear  light, 
and  the  light  portions  dark,  in  the  picture.  By  copying 
the  copy,  a  true  representation  of  the  original  device, 
called  a  "  positive  picture,"  is  obtained.  Both  the  "  pos- 
itive" and  "  negative"  are  soon  destroyed  by  the  action 
of  light  upon  the  whole  sensitive  surface.  But  the 
means  exist  for  rendering  them  entirely  permanent  in 
any  exposure. 


H  X  Y 


COUNTERFEITING.  331 

842.  THE  SILVER  SOLUTIONS. — To  prepare 

How  is  the  sil- 
ver solution       the  silver  solution,  above  required,  put  a 

prepai  three  cent  piece  into  a  test-tube,  having  a 

diameter  a  little  larger  than  the  coin  itself.  Then  fill  the 
tube  to  the  depth  of  an  inch,  with  a  mixture  of  equal 
parts  of  nitric  acid  and  water.  The  solution  of  the  coin 
commences  immediately.  When  it  is  completed,  fill 
up  the  tube  with  water,  mix  well  by  shaking,  and  the 
solution  is  ready  for  use.  For  the  same  quantity  of 
salt  solution,  enough  common  salt  to  fill  about  two- 
thirds  of  an  inch  of  the  tube,  may  be  used. 

843.  ANASTATIC  PRINTING. — This  name 

Describe 

briefly  the  is  given  to  a  process  by  which  any  kind 
astatic  print-  °^  Panted  matter,  may  itself  be  converted 
illO ?  into  a  plate,  from  which  new  copies  may  be 

printed.  It  consists,  essentially,  in  the  transfer  of  the 
letters,  or  other  design,  to  zinc,  by  pressure,  the  paper 
having  been  previously  moistened  by  dilute  acid. 
The  oil  of  the  ink  remains,  and  the  paper  is  re- 
moved. The  zinc  plate  is  then  used,  like  an  ordi- 
nary lithographic  stone.  When  the  inked  roller  is 
passed  over  it,  the  ink  only  adheres  to  the  design,  from 
which  an  impression  may  then  be  taken  by  the  ordi- 
nary process. 

What  is  said  of  844  COUNTERFEITING. — Bank  notes  may 
counterfeiting  fa  counterfeited  by  either  of  the  above 

by  the  above 

process?  processes.     Great  apprehension    has  been 

felt,  test  they  should  render  the  use  of  paper  money  en- 
tirely insecure.  An  effectual  means  of  protection 
against  such  counterfeiting,  has  recently  been  devised.* 

*  Serop van's  patent. 


332  SALTS. 

Copying  by  the  anastatic  process,  obviously  depends 
upon  the  absence  of  oil  from  the  back  ground  of  the 
picture.  The  employment  of  an  oil  tint,  instead  of 
blank  paper,  for  the  back  ground,  is  therefore  a  perfect 
security  against  it.  Counterfeiting  by  the  photographic 
process  depends  on  the  fact,  that  the  light  which  falls 
on  a  picture  is  intercepted  by  the  dark  letters.  If  they 
are  printed  in  a  transparent  blue,  the  chemical  rays 
are  permitted  to  pass  through  the  printed  as  well  as  the 
imprinted  portions.  A  copy  with  the  contrasts  of  the 
original  picture  is  thereby  rendered  impossible.  By 
printing  with  blue  ink,  on  a  back  ground  of  some  other 
color,  both  of  the  securities  against  counterfeiting 
above  mentioned,  are  combined. 


CHEMICAL  ANALYSIS. 
845.  DIRECT  METHOD. — In   the   process 

Describe  anal- 
ysis by  sol-        of  analysis,  advantage  is  taken  of  the  dis- 
tinguishing   properties    of  different    sub- 
stances, to  effect  their  detection  and  separation.     They 
may  sometimes  be  separated  by  the  employment  of  a 
solvent  which  acts  upon  one,  and  leaves  the  other  mi- 
dissolved.     The  separation  of  silver  from   gold  in  the 
process  of  assaying,  is  a  case  in  point. 
Describe  di-  846.  A  more  common  method  is  to  bring 

rect  analysis      tne    wnole   substance   into   solution,    and 

oy  precipita- 
tion, afterward  separately  to  precipitate  its  sev- 
eral constituents,  by  agents  which  have  no  effect  upon 
the  rest.     The   separation  of  alumina  from  lime   may 
serve  as  an  example.     A  mixture  of  the  two  being  dis- 


CHEMICAL    ANALYSIS.  333 

solved  in  acid,  the  former  may  be  precipitated  by  am- 
monia. The  latter  remains  in  solution  and  may  be 
afterward  removed  by  some  other  agent. 

847.  INDIRECT  METHODS. — Indirect  me- 

II  lust  rate  the  ,  ,  - 

indirect  mcth-  thods  of  analysis  are  much  more  frequently 
od-  employed  than  either  of  the  above.  The 

detection  of  silver  in  a  copper  alloy  may  serve  as  an 
example.  The  alloy  being  first  dissolved,  hydrochloric 
acid  is  added  to  the  solution,  as  a  test.  The  appearance 
of  a  white  insoluble  curd,  is  taken  as  conclusive  evi- 
dence of  the  presence  of  silver.  No  other  metal  of  an 
alloy  ever  combines  with  the  chlorine  of  hydrochloric 
acid  to  form  such  a  precipitate.  The  evidence  is  quite 
as  satisfactory  to  the  chemist  as  that  which  would  be 
obtained  by  the  separation  of  the  silver  in  the  metallic 
form. 

848.  Neither  is  separation  necessary,  in 

How  is  the  . 

weight  calcu-  order  to  ascertain  the  exact  weight  of  the 
lated?  metal  which  has  been  precipitated.  Ad- 

vantage is  here  taken  of  the  well-established  law  of 
combination  by  definite  proportions.  The  chloride  of 
silver  produced  in  the  experiment,  is  invariably  of  the 
same  proportional  composition.  It  is  made  up  of  an 
atom  of  silver,  to  every  atom  of  chlorine.  Its  weight 
being  ascertained  by  the  balance,  the  amount  of  silver 
which  it  contains  may  be  calculated  with  absolute  pre- 
cision, by  help  of  the  table  of  atomic  weights.  This 
weight  being  compared  with  that  of  the  original  alloy, 
gives,  by  a  simple  calculation,  the  per  centage  propor- 
tion of  silver  which  the  alloy  contains.  The  nature  and 
quantity  of  other  constituents,  whether  of  compounds 


334  CHEMICAL   ANALYSIS. 

r 

or  mixtures,  is  determined  by  processes  analogous  to 
these  which  have  above  been  described. 

849.  SEPARATION  INTO  GROUPS. — In  the 
Nation  into1  analysis  of  substances  containing  many  con- 
groups effect-  stituents,  a  separation  into  groups,  precedes 
the  isolation  of  the  individual  constituents. 
This  is  effected  by  the  use  of  certain  agents,  in  suc- 
cession, which  have  the  property  of  precipitating  whole 
groups.  These  being  again  dissolved,  are  commonly 
subdivided  into  smaller  groups  by  similar  means.  The 
detection  and  separation  of  the  individual  constituents 
is  finally  accomplished  by  means  already  described. 
Some  general  idea  of  the  process  of  inorganic  analysis 
may  be  obtained  from  the  foregoing.  Particulars  upon 
this  subject  must  be  sought  in  works  on  analytical 
chemistry. 


335 


TV. 

ORGANIC  CHEMISTRY. 


CHAPTER  I. 

GENERAL  VIEWS. 
850.  DEFINITION. — Organic  chemistry  is 

Of  what  does  .    .  . 

organic  chem-  that  division  of  the  science  which  treats 
istry  treat  ?  Qf  substances  of  animal  or  vegetable  ori- 
gin. Starch,  wood,  gums,  and  resins  ;  the  juices,  colo- 
ring matters,  and  fragrant  principles  of  plants;  the 
blood  and  flesh  of  animals  ;  all  come  under  its  conside- 
ration. The  process  of  germination,  in  which  the 
plant  first  comes  to  be  a  living  thing  ;  the  processes  of 
decay  and  putrefaction,  in  which  it  returns  again  to  the 
earth  and  atmosphere,  are  also  to  be  treated  under  this 
division  of  the  subject.  Most  organic  forms  of  matter 
experience  peculiar  changes,  and  are  converted  into 
new  substances  by  chemical  means.  The  products  of 
such  transformations  belong  also  to  organic  chemistry.* 
851.  VARIETY  OF  ORGANIC  MATTER. — 

Illustrate  the  .  f  . 

variety  of  or-  The  variety  of  organic  matter  is  almost 
garde  matter.  wjthout  limit.  Every  color  of  every  dye, 
every  flavor  of  every  sweet  or  bitter  herb,  every  gum, 

*  Carbonic  acid,  water,  bone  ash,  and  some  other  substances,  are  ex- 
ceptions to  the  above  rule,  and  are  commonly  treated  under  the  head 
of  inorganic  chemistry.  Though  often  produced  from  animal  and 
vegetable  substances,  they  also  exist,  ready  formed,  in  nature,  or  may 
be  readily  made  from  organic  or  mineral  matter. 


336  ORGANIC    CHEMISTRY. 

and  every  resin,  is  a  distinct  organic  substance.  In 
the  animal  body,  also,  there  is  scarcely  less  variety. 
The  fluids  which  dissolve  the  food,  the  blood  which 
distributes  it  throughout  the  body,  the  color  which  tints 
the  skin  aiid  hair,  and  the  milk  "which  nourishes  the 
young,  are  a  few  of  the  substances  which  it  includes. 

852.  MATERIALS  OF  VEGETABLE  GROWTH. 

What  arc  the      „-..,'  -    . 

materials  of       With  the  exception  of  the  small  proportion 
°^  mmeral  matter  which  is  derived  from 


the  earth,  the  materials  out  of  which  all 
animal  and  vegetable  matter  is  formed,  are  but  few  in 
number.  Carbonic  acid,  ammonia,  and  water,  are  all. 
These  are  partly  obtained  from  the  air,  and  partly  from 
the  earth.  Carbon,  hydrogen,  oxygen,  and  nitrogen, 
are  the  four  elements  which  enter  into  their  compo- 
sition. 

What  is  re.-  853.    CONVERSION  OF  THE  MATERIALS.  - 

workable  in      A   vital  force  slumbers  within  the    seed, 

the  new  pro-  ,  .  ,, 

parties  which     which  in  germination  wakes  to  life.     Call- 

result  ?  jng  to  -tg    aj^  faQ  ijgjlt  an(j  Warmtl1  Of   the 

sun,  it  weaves,  as  it  were,  out  of  the  scanty  mate- 
rials which  have  been  mentioned,  all  of  the  varied 
forms  of  vegetable  matter.  Among  the  materials,  one 
is  a  tasteless  solid  ;  the  rest  are  tasteless  gases.  Yet 
sweet,  sour  and  bitter  flavors  result  from  their  combi- 
nation, with  all  the  other  boundless  variety  of  the  or- 
ganic world. 

854.   SIMILARITY  OF  COMPOSITION.  —  Yet 

Give  some  in-  , 

stances  of  aim-  more  remarkable  than  the  limited  number 

il^olidth  of  elemeilts>  fr°m  which  so  great  a  variety 

di/f  rent  pro-  of   organic  substances    is   formed,    is   the 

per  similarity  of   composition   in  many  sub- 


GENERAL    VIEWS.  337 

stances,  which  are  yet  so  widely  different  in  their  pro- 
perties. Vinegar  differs  from  alcohol,  for  example,  in 
containing  a  little  more  oxygen  and  a  little  less  hydro- 
gen, while  the  proportion  of  carbon  in  each  is  the  same. 
Ether,  also,  contains  the  same  amount  of  carbon  as  the 
alcohol  from  which  it  is  formed,  with  a  little  less  hydro- 
gen and  oxygen.  Yet  these  substances  are  all  widely 
different  in  their  properties. 

Mention  some  855.      IDENTITY    OF    COMPOSITION. Most 

™hich™r*difi  remarkaole  °f  all>  and  at  first  view  incred- 
ferent  in  pro-  ible,  is  the  fact  that  many  organic  sub- 
tdenticaHn  stances  which  are  as  widely  different  in 
composition.  properties  as  any  which  have  been  named, 
are  still  precisely  the  same  in  their  composition  ;  not 
alone  containing  the  same  elements,  but  containing 
them  in  precisely  the  same  proportion.  The  most  careful 
chemical  investigation  finds  no  difference  of  composition 
in  wood,  gum,  and  starch.  The  sugar  which  sweet 
milk  furnishes,  arid  the  acid  which  exists  in  the  sour, 
contain  identically  the  same  proportions  of  the  same 
constituents.  The  oils  of  turpentine,  lemon  and  pepper, 
so  different  in  their  taste,  contain  an  equal  quantity  of 
carbon  and  hydrogen,  without  the  addition  of  any 
third  substance  to  either,  to  account  for  the  difference. 
Truly,  organic  chemistry  has  brought  us  to  results  as 
strange  as  the  dream  of  the  alchemist,  who  believed 
that  lead  might  be  converted  into  silver,  and  copper 
into  gold.  All  such  substances,  possessing  the  same 
composition  with  different  properties,  are  called  iso- 
meric  bodies — a  term  signifying  their  similarity  of  com- 
position. 

15 


338  ORGANIC    CHEMISTRY. 

856.  ARRANGEMENT  OF  ATOMS. — At  a  loss 

How  are  the 

above  facts  ac-  for  any  other  way  of  accounting  for  such 
counted  for?  difference  of  properties,  we  are  compelled 
to  believe  that  it  is  because  of  difference  of  atomic 
arrangement.  We  have  seen,  in  the  case  of  iodide 
of  mercury,  mentioned  in  a  former  chapter,  that  a 
mere  touch,  which  produces  motion  and  re-arrange- 
ment of  its  atoms  in  smaller  groups,  at  the  same  time 
changes  the  color  of  the  compound  from  yellow  to  red. 
Now  the  molecule  of  lactic  acid,  although  containing 
the  same  relative  proportion  of  all  of  its  constituents, 
is  smaller  than  the  molecule  of  sugar  of  milk.  It  con- 
tains six  atoms  of  carbon,  six  of  hydrogen,  and  six  of 
oxygen.  The  molecule  of  sugar  of  milk  contains 
twelve  of  each,  and  can  therefore  furnish  material  to 
make  two  of  acid,  as  it  does  in  the  souring  of  milk. 
And  we  may  suppose  that  the  change  from  sweet  to 
sour  is  owing  to  this  subdivision  of  the  molecules. 

857.  There  are  other  cases  of  identical 

How  is  diver-  .       ,          .         -,  •   -,  •  T  rr 

sity  of  prop-  composition,  in  which  there  is  no  difference 
€countedfor  whatever  in  the  size  of  the  molecule,  or  the 

when  there  is  number  of  atoms  which  enter  into  its  corn- 
no  difference  .  .  .  .,  ., 

of  compost-  position.  This  is  the  case  with  the  oils  of 
tionor  size?  turpentine,  lemon,  and  pepper,  and  perhaps 
with  wood,  starch,  and  sugar.  The  molecules  of  each 
are  composed,  not  alone  of  the  same  proportion  of  the 
elements  which  enter  into  its  composition,  but,  as  there 
is  reason  to  believe,  of  the  same  number  of  atoms  of 
each.  We  are  therefore  compelled  to  look  for  the  differ- 
ence which  shall  account  for  their  peculiar  property,  in 
a  different  arrangement  of  atoms,  inside  of  the  mole- 


GENERAL    VIEWS.  339 

cules  themselves.  A  more  satisfactory  idea  of  this  sub- 
ject can  be  obtained  after  reading  what  follows,  on  the 
subject  of  organic  radicals. 

Give  an  in-  858.     SUBSTITUTION.  —  A  still  more  re- 

stance  of  sub-    markable  evidence  of  the  influence  of  ar- 

stitution  titat 

does  not  affect  rangement  or  grouping  of  atoms,  remains 
P10PC^  to  be  mentioned.  The  internal  arrange- 

ment of  a  molecule  remaining  the  same,  it  seems  to 
matter  little,  in  many  cases,  of  what  it  is  composed. 
Hydrogen  may  even  be  replaced  by  chlorine,  a  body 
as  widely  different  from  it  as  anything  which  nature 
affords.  By  this  means,  ordinary  acetic  acid  is  con- 
verted into  chloracetic  acid,  a  body  remarkably  anal- 
ogous in  its  properties  to  the  acid  from  which  it  is 
formed.  From  this,  again,  by  withdrawing  the  chlo- 
rine and  restoring  the  hydrogen,  the  original  acetic  acid 
is  reproduced. 

859     TYPES.  —  The    last  example   will 

What  in  said  .  •, 

of  the  doctrine    serve  as  an  illustration  of  the  doctrine  of 


cnemical  types  and  substitution,  which  cer- 
tain chemists  have  endeavored  to  extend  to 
all  organic  bodies.  It  has  been  maintained  that  the 
properties  of  these  bodies  depend  solely  upon  arrange- 
ment, without  any  reference  to  the  nature  of  the  ele- 
ments combined.  The  fact  is,  that  while  there  are 
many  cases  of  such  substitution  without  essential 
change  of  properties,  it  is  always  attended  by  more  or 
less  modification  of  the  original  substance.  The 
properties  of  a  compound  are  therefore  to  be  regarded 
as  depending  neither  upon  the  nature  or  arrangement 
of  atoms  alone,  but  upon  both  causes  combined.  The 


340  ORGANIC    CHEMISTRY. 

type,  is  the  group  which  remains  permanent,  while  the 
individual  atoms  which  compose  it  are  changed. 

860.  COMPOUND    RADICALS. — Many  or- 

Ilhistrate  the  ' 

subject  of  com-  game  bodies,  although  compounds,  com- 
Pcahd  Tadl'  Port  themselves  as  if  they  were  elementary 
substances.  Some  of  these  are,  as  it  were, 
metals  ;  forming  oxides,  chlorides,  and  salts,  like  the 
true  metals,  which  have  already  been  considered. 
Others  correspond  more  nearly  to  the  metalloids.  Each 
being  organic,  and  like  a  metalloid,  the  root  of  a  whole 
series  of  compounds,  is  called  an  organic  radical.  The 
term  radical  is  sometimes  applied,  for  similar  reasons,  to 
chlorine,  bromine,  and  other  elementary  substances. 
As  the  organic  substances  above  referred  to,  are  com- 
posed of  different  elements,  they  are  called  compound 
radicals. 

861.  ILLUSTRATION. — A  molecule  of  or- 
ple  of  acom-     dinary  ether  is  composed  of  four  atoms  of 
poundradical    carborij  five  of  hydrogen,  and  one  of  oxy- 
gen.    But  the  carbon  and  hydrogen  atoms  are  grouped 
together,    forming  a   compound  radical  called  ethyle, 
with  which  the  oxygen  is  then  com- 
bined to  form  ether  or  oxide  of  ethyle. 

Alcohol,  as  illustrated  in  the  figure,  is 
the  hydrated  oxide  of  this  radical.  Al- 
dehyde, a  substance  to  be  hereafter  more  particularly 
described,  has  the  same  composition  as  alcohol,  with 
the  exception  that  two  atoms  of  hydrogen  have  been 
removed  from  the  radical.  Acetic  acid  is  formed  from 
aldehyde  by  the  re-placement  of  the  removed  hydrogen 
by  the  same  number  of  atoms  of  oxygen.  Ethyle  itself 
may  be  prepared  indirectly  from  the  oxide,  as  potassium 


HOMOLOGOUS    SERIES.  341 

is  obtained  from  potassa  or  oxide  of  potassium,  although 
by  a  different  process. 

What  were  the        862.    It  is  but  a  few  years  since  the 
grounds  of  be-    metf10(i  of  producing  ethyle  was  discovered, 

hef  vn  the  ex-  &          J 


of         but  chemists  believed  in  its  existence  al- 
most  as  confidently  before,  as  now.     They 
co-eery?  reasoned  that  ether,  which  possesses   the 

properties  of  an  oxide,  must  have  its  radical,  as  Sir 
Humphrey  Davy  reasoned  that  potassa,  soda  and  lime, 
must  each  contain  its  metal. 

863.  HOMOLOGOUS    SERIES.  —  Certain    of 

What  are  ho-  «.<>'•'•« 

moiogous  these  compound  radicals  sustain  to  each 
other  a  curious  numerical  relation.  They 
form  a  series  in  arithmetical  progression,  differing  from 
each  other  in  composition,  by  a  common  difference. 
Two  atoms  of  carbon  with  two  of  hydrogen  forms  the 
common  difference  of  the  series  referred  to.  Methyl, 
the  radical  of  wood  spirit,  begins  the  list  with  two  atoms 
of  carbon  and  three  of  hydrogen.  Ethyle  follows  —  its 
composition  being  expressed  by  the  addition  of  the 
common  difference  to  the  last.  Margaryl,  a  radical 
contained  in  certain  fats,  is  the  seventeenth  member  of 
the  series.  Each  of  these  radicals  has,  like  ethyle,  its 
own  oxide  or  ether,  its  hydrated  oxide  or  alcohol  ;  also 
its  aldehyde  and  its  acid.  A  series  of  radicals,  ethers, 
alcohols,  aldehydes  and  acids,  each  in  arithmetical  pro- 
gression, is  thus  produced.  Such  series  are  called  ho- 
mologous. 

864.  PRODUCTION.  —  There  are  many  saps 

How  are  the  *  *- 

different  mem-  in  most  of  the  series,  but  the  law  of  their 
bersproduccd?  progression  is  so  we]1  established,  that  no 


342  ORGANIC    CHEMISTRY. 

doubt  can  exist  as  to  the  probable  production  of  the 
missing  members.  The  most  complete  of  the  series  is 
given  in  the  Appendix.  Several  of  its  more  simple 
members  may  be  produced  by  the  action  of  nitric  acid 
upon  those  higher  in  the  scale.  The  acid  has  the  effect 
of  burning  out  part  of  their  carbon  and  hydrogen,  and 
thus  reducing  the  relative  proportion  of  their  constitu- 
ents. 

865.  PROGRESSION    OF    PROPERTIES. — 

What  is  said 

of  the  relation    There  is  also  a  similar  progression  of  pro- 

°~        PertieS    in    the    SerieS'       The    earlier    menl- 

bers  of  the  alcohol  series  are  highly  vol- 
atile liquids;  the  later  are  solids  at  ordinary  tempera- 
tures. Each  increase  of  the  relative  properties  of  car- 
bon and  hydrogen  produces  a  substance  which  is  more 
fixed.  In  other  words,  the  boiling  point  is  higher  for 
each  successive  member.  The  difference  for  each  is 
about  34°  F.  The  density  of  the  vapors  increases  by 
a  similar  law.  It  is  thus  possible  to  predict,  with  accu- 
racy, the  boiling  point  and  density  of  vapor  in  members 
of  the  series  which  have  not  yet  been  discovered. 

866.  RADICALS    NOT    ISOLATED. — The 

Have  all  or-  . 

ganic  radicals  larger  part  of  the  organic  radicals  have  not 
been  isolated?  yet  ^een  isolated.  They  are  only  known 
in  their  compounds,  and  the  belief  in  their  existence 
rests  on  the  reasoning  which  has  been  given  in  a  previ- 
ous paragraph.  This  is  regarded  by  chemists  as  abun- 
dantly sufficient  for  giving  them  names  and  places 
among  chemical  compounds.  It  is  still,  however,  to 
be  borne  in  mind,  that  the  reasoning  is  not  of  the  nature 
of  absolute  demonstration. 


SUBSTITUTIONS.  343 

Mention  some  >    SUBSTITUTION    COMPOUNDS. It  Was 

instances  of      stated,  in  a  previous  paragraph,  that  there 

the  substitu-  .,        ,  ,,     .          .     - 

tionofradi-  are  many  cases  of  substitution  of  the  ele- 
cals'  ments  for  each  other,  without  material 

change  of  properties.  Certain  cases  of  substitution  of 
organic  radicals  for  the  elements  remain  to  be  men- 
tioned. Theoretically  considered,  they  form,  perhaps, 
the  most  important  discoveries  which  have  for  years 
been  made  in  organic  chemistry.  Ammonia,  as  the 
student  is  already  informed,  is  a  volatile  base  whose 
molecules  consists  of  one  atom  of  nitrogen  and  three 
atoms  of  hydrogen.  For  one  of  these  atoms  of  hydro- 
gen, a  molecule  of  the  radical  ethyle  may  be  substituted, 
without  very  materially  affecting  its  properties.  The 
new  ammonia  thus  formed  is,  like  the  first,  a  volatile 
base  resembling  the  first  so  nearly  in  odor  that  it  must 
have  been  repeatedly  mistaken  for  it  when  accidentally 
produced.  It  is,  however,  a  liquid  at  ordinary  temper- 
atures. This  body  has  received  the  name  of  etliyla- 
mine.  Methylamine  is  another  body  of  the  same  series, 
produced  by  the  replacement  of  two  of  the  atoms  of  am- 
monia by  the  radical  ethyl.  Triethylamine  is  a  third. 
By  a  similar  substitution  of  hydrogen  in  ammonia  by 
the  radical  methyl,  another  series  is  produced.  Other 
radicals  yield  other  series. 

868.  OTHER  SUBSTITUTIONS. — There  are 

Mention  other 

cases  of  sub-  other  bodies  which  result  from  the  substi- 
stitution.  tution  of  different  radicals  or  the  metal  pla- 
tinum, for  the  different  atoms  of  hydrogen.  Substitu- 
tions may  even  exist  in  the  substituting  radicals.  All 
of  these  bodies  retain  the  type  of  ammonia,  and  all  of 


344  ORGANIC    CHEMISTY. 

them  have  basic  properties.  Many  of  them  are  strikingly 
similar  to  ammonia  in  odor  and  other  properties.  These 
substitution  compounds  afford  still  further  evidence  of 
the  influence  of  arrangement  of  atoms  and  molecules 
in  determining  the  character  of  chemical  compounds. 
Many  of  these  bodies  differ  very  widely  in  their  com- 
position, and  are  yet  closely  allied  in  their  properties. 
The  methods  of  producing  the  substitutions  above 
mentioned,  are  not  of  interest  to  the  general  student. 
A  general  notion  of  substitutions  may  be  obtained  from 
the  double  decompositions  with  which  the  student  is 
already  familiar. 


ORGANIC    CHEMISTRY. 


345 


CHAPTER  II. 


VEGETABLE  CHEMISTRY. 


What  is  mid         869.  GERMINATION. — Before  the  process- 
of  germination    es  of  transformation  of  the  materials  of  the 

and  the  chan-  ... 

ges  which  at-  earth  and  atmosphere  into  the  innume- 
rable products  of  the  vegetable  world  can 
commence,  a  rudimental  plant  must  be  developed  from 
the  seed.  The  seed  itself  contains  the 
materials  for  its  production.  These  are 
principally  starch,  and  gluten,*  or  the  other 
substances  analogous  to  each,  which  have 
already  been  described.  The  first  stage  in 
the  process  is  the  absorption  of  moisture 
and  oxygen  from  the  air,  and  the  conse- 
quent production  of  diastase^  This  sub- 
stance has  the  remarkable  property  of  con- 
verting starch  into  sugar,  and  rendering  soluble  all  of 
the  remaining  gluten  of  the  seed.  By  the  appropria- 
tion of  these  materials,  which  have  been  stored  up  for 
it  in  the  seed,  the  germ  is  developed  into  a  perfect 
plant.  It  lets  down  its  root  into  the  soil  in  search  of 

*  Gluten  is  the  stringy  substance  which  remains  on  removing  the 
starch  from  dough  by  long  continued  kneading.  It  is  further  described 
in  a  subsequent  paragraph. 

f  Diastase  is  an  oxydized  gluten,  which  is  always  produced  from 
gluten  in  germination. 

15* 


346  ORGANIC    CHEMISTRY. 

mineral  food,  and  lifts  its  leaves  into  the  atmosphere, 
from  which  it  is  to  derive  its  principal  nourishment.  At 
this  point,  the  true  vegetative  process  commences. 

870.     VEGETABLE    NUTRITION. — Every 

What  is  the 

office  of  leaves  leaf  is  a  net  to  catch  the  fertilizing  con- 
°^  p  a  stituents  of  the  air,  and  appropriate  them 

to  the  uses  of  the  plant.  It  drinks  them  in  through  its 
countless  pores,  while  the  root  supplies  the  remaining 
material  and  sends  it  upward  in  the  rising  sap.  All  of 
these  materials  meet  in  the  leaf,  which  is  the  labora- 
tory in  which  their  conversion  into  vegetable  matter  is 
to  be  accomplished.  The  light  and  heat  of  the  sun 
co-operate  with  the  vital  forces  of  the  plant,  in  the 
transformation  which  succeeds. 

871.  Whatever  proportion  of  carbonic 
evohed from  acid  and  water  may  be  employed  as  the 
plants?  raw  material,  it  is  obvious,  by  comparison 

of  their  composition  with  that  of  vegetable  substances, 
as  hereafter  given,  that  the  oxygen  is  furnished  in 
larger  quantity  than  is  required.  Water  alone  supplies 
a  sufficient  quantity  of  this  element,  and  more  than 
enough  for  most  substances  that  are  to  be  formed.  As 
the  process  of  transformation  proceeds,  this  gas  is  there- 
fore constantly  thrown  off  into  the  air.  It  is  the  refuse 
of  the  manufacture.  Inasmuch  as  the  evolution  takes 
place  from  the  leaf  and  other  green  parts  of  the  plant, 
it  is  reasonable  to  suppose  that  this  is  the  point  where 
the  process  of  transformation  is  principally  conducted. 
The  gum,  sugar,  or  other  materials  produced,  are  dis- 
solved in  the  descending  sap,  and  transformed  into 
other  products,  in  the  course  of  their  circulation. 


OFFICE    OF    THE    ROOT.  347 

872.    The   agency   of  the   leaves   of 

the  , 

of  plants  in  absorbing  and  decomposing  car- 
ro-  bonic  acid>  may  be  illustrated  by  the  simple 
ved  by  experi-  means  represented  in  the  figure.  A  glass 
funnel  being  filled  with  leaves,  and  slightly 
carbonated  water,  is  exposed  to  the  sun. 
Oxygen  gas  is  gradually  evolved  from 
the  absorption  and  decomposition  of  the 
carbonic  acid,  and  collects  in  the  tube 
of  the  funnel.  The  oxygen  may  be 
tested  by  the  usual  means.  The  inversion  of  the  fun- 
nel without  loss  of  its  contents,  is  easily  effected,  by 
covering  it  with  a  saucer  and  turning  it  in  a  pail  of 
water. 

873.  For  certain  transformations  of  ma- 

What  trans-  .  .  . 

formations  oc-    terial  in  plants,  the  evidence  is  entirely  con- 

purin  plant*?     clusiye>       The    sugar   beet    and    tumip    are 

sweetest  in  the  earlier  stages  of  their  growth.  Later 
in  the  year  they  become  hard  and  fibrous.  This  change 
is  undoubtedly  owing  to  the  conversion  of  the  sugar, 
contained  in  the  sap,  into  woody  fibre.  In  the  ripening 
of  grain,  the  sweet  and  milky  juice  of  the  young  plant 
is  converted  into  starch.  Both  hay  and  grain,  which 
are  harvested  too  late,  are  deteriorated  by  the  conver- 
sion of  a  portion  of  their  starch  and  sugar  into  wood. 
In  the  ripening  of  fruits  a  portion  of  their  acid  is  con- 
verted into  sugar,  as  is  evident  from  their  change  of  flavor. 

874.  OFFICE  OF  THE  ROOT. — The  agency 
How  w  the  ac-    of  fae  roots  m  supplying  the  plant  with  its 

tion  of  the 

roots'illus-  mineral  food,  may  be  illustrated  by  the 
apparatus  represented  in  the  figure.  In 
preparation  for  the  experiment,  a  glass  fun- 


348  ORGANIC    CHEMISTRY. 

nel  is  tightly  covered  with  a  piece  of  blad- 
der, and  then  filled  with  a  solution  of  sugar 
or  salt.  A  tube  is  then  fitted,  air  tight,  to 
its  extremity.  A  glass  vial,  from  which 
the  bottom  has  been  removed,  may  be  sub- 
stituted for  the  funnel  in  this  experiment. 
On  placing  the  apparatus,  thus  arranged,  in  a 
vessel  of  water,  the  latter  penetrates  the  ani- 
mal membrane,  and  adds  itself  to  the  con- 
tents of  the  funnel.  The  flow  of  the  water 
is  called  endosmose,  and  is  made  apprecia- 
ble to  the  eye  by  the  rise  of  liquid  in  the  tube.  An 
cxosmose,  or  flow  of  a  small  portion  of  the  contents  of 
the  funnel  outward,  takes  place  at  the  same  time. 

875.  The  phenomenon  exhibited  in  the 

Explain  the  . 

phenomenon  above  experiment,  is  to  be  accounted  for 
of  endosmose.  by  the  difference  of  capil]ary  attraction  in 

the  bladder  for  the  two  liquids.  The  spongioles,  with 
which  the  extremities  of  the  roots  are  provided,  being 
filled  with  solutions  of  gum  and  sugar,  act  similarly 
upon  the  liquids  of  the  soil.  The  endosmotic  action, 
above  described,  is  not  confined  to  the  roots  of  plants, 
but  occurs  in  all  their  organs,  through  the  walls  of  the 
minute  cells  of  which  they  are  composed.  In  connec- 
tion with  the  transpiration  of  water  from  the  leaves, 
it  is  probably  the  principal  cause  of  the  circulation  of 
the  sap.  The  relation  of  the  plant  and  soil  is  further 
considered  in  a  subsequent  chapter. 

876.  CONSTITUENTS  OF  PLANTS. — Amoner 

Mention  some 

of  the  more  the  more  important  of  vegetable  substances 
ffSea^Ve'  are  wood,  starch,  sugar  and  gluten.  Woody 
stances.  fibre  forms  the  mass  of  the  plant ;  starch 


WOOD.  349 

and  gluten  collect  in  the  seed  j  while  sugar  and  gum 
exist  principally  in  the  sap  and  fruit,  or  exude  from 
the  bark. 


WOOD. 
Mention  dif-  S77'      W°ODY    FIBRE.— Woody  fibre,    of 

ferent forms      which  the  fibrous  threads  of  cotton  or  flax 

of  ivoody  fibre  ,  j      /r 

^-its  com-  maY  serve  as  an  example,  is  composed  of 
position.  carbon,  hydrogen  and  oxygen.  Its  mole- 

cule contains  twelve  atoms  of  carbon,  to  ten  of  hydro- 
gen and  ten  of  oxygen.  It  constitutes  the  solid  mass 
of  all  vegetable  organs,  whether  hard  and  firm,  like 
the  fibre  of  the  oak  ;  soft,  like  the  pulp  of  fruits  ;  or 
fibrous,  like  cotton  and  flax.  In  one  or  the  other  of 
its  forms  it  therefore  serves  us  for  shelter,  clothing  and 
food.  It  forms  in  plants  the  cells  in  which  the  vege- 
table juices  are  contained,  and  the  veins  or  pores 
through  which  they  circulate  ;  and  has  thence  received 
its  name  of  cellulose.  In  wood,  these  cells  are  often 
lined  or  filled  with  a  substance  of  similar  composition, 
to  which  the  name  of  lignin  has  been  given. 

878.  CHANGE  BY  HEAT — GAS,  CHAR- 
changed  by  COAL,  ETC. — Under  the  influence  of 
heat?  a  high  temperature,  without  access 

of  air,  wood  is  converted  into  charcoal,  water, 
gases,  wood  vinegar,  and  tar.  It  is  to  be  observed 
that  this  change  is  the  simple  result  of  a  re-ar- 
rangement of  the  atoms  of  the  wood  itself,  with- 
out the  help  of  additional  oxygen  or  other  ele- 
ments. It  is  a  most  remarkable  instance  of  va- 


350 


ORGANIC    CHEMISTRY. 


riety  as  produced  by  varied  arrangement.  The  new 
substances  are,  as  it  were,  different  patterns,  woven 
from  the  same  colored  threads.  The  gases,  of  which 
carbonic  acid,  light  and  heavy  carburetted  hydrogen 
are  the  principal,  have  been  already  described.  Wood 
vinegar  and  wood  tar  form  the  subjects  of  subsequent 
paragraphs.  An  excess  of  carbon  remains  behind  as 
charcoal.  The  process  is  called  dry  distillation.  The 
decomposition  may  be  illustrated  with  saw-dust,  in  a 
test  tube,  as  previously  described. 

879.  SIMILAR  CHANGE  IN  NATURE — PEAT. 

Mention  a  si-  . 

milar  change  Peat  is  formed  by  the  decay  of  vegeta- 
tn  nature.  j}je  matter  un(}er  water.  The  green  slime 

which  forms,  in  the  summer,  upon  stagnant  water,  is 
composed  of  minute  plants.  These  die,  each  season, 
and  sink  to  the  bottom,  until,  in  the  course  of  years  or 
ages,  vast  accumulations  of  vegetable  matter  are  the 
result.  By  their  partial  decay  or  putrefaction  under 
water,  they  are  converted  into  peat.  The  process  is 
analogous  to  that  of  dry  distillation,  and  the  products 
similar.  Carbonic  acid  and  carburetted  hydrogen  gases 
are  evolved,  while  a  solid  residue  of  peat  remains  be- 
hind. It  may  be  regarded  as  a  half-formed  charcoal. 
Peat  contains,  in  addition  to  its  carbon,  a  little  hydro- 
gen and  a  still  smaller  proportion  of  oxygen.  The 
carbonic  acid  evolved  in  the  above  process,  often  makes 
its  way  to  the  surface,  at  some  neighboring  locality, 
in  the  form  of  mineral  springs. 

880.  BITUMINOUS  COAL. — The  formation 

How  is  bitutm-        . ,  .  ,  . 

nous  coal  01  bituminous  and  anthracite  coal  is  a  con- 
formed?  sequence  of  a  similar  decay  of  vast  accu- 


WOOD.  351 

mulations  of  vegetable  matter,  which  have  been  buried 
in  the  earth  during  previous  ages  of  its  existence.  As 
a  consequence  of  pressure,  the  material  takes  a  different 
form  from  that  already  described,  and  is  found,  after 
ages  have  elapsed,  as  bituminous  coal. 
Howisanthra-  881.  ANTHRACITE  COAL. — Where  bitu- 
dte  formed?  mous  coai  has  been  subjected  to  great  heat, 
more  carbon  and  hydrogen  are  expelled,  and  anthracite 
coal  remains.  A  similar  change  takes  place  where  bi- 
tuminous coal  is  heated  by  artificial  means.  The  coke 
which  remains,  is,  like  anthracite  coal,  nearly  pure  car- 
bon. 

882.  PRODUCTION   OF  HUMUS. — Humus, 

What  is  hu- 
mus?  How  is    or  the  vegetable  mould  of  forests,  is  formed 

it  produced?        by  the  decay  of  wood  Qr  yegetable  matter 

in  the  air.  Such  decay  is  a  species  of  slow  combus- 
tion. The  carbon  is  more  slowly  consumed  than  the 
other  constituents.  The  vegetable  mould  or  humus 
which  remains  after  the  partial  decay,  is,  therefore,  like 
peat,  much  richer  in  carbon  than  the  material  from 
which  it  was  produced.  It  is  variable  in  composition, 
according  to  the  progress  of  the  decay.  The  access 
of  oxygen  from  without  being  unlimited,  it  is  found  to 
remain  in  equal  atomic  proportion  with  the  hydrogen. 

What  is  the  883.       WHITE      ROTTEN     WOOD. White 

composition  of  roUen  wood,  which  forms  in  stumps  and 

wliite  rotten 

wood?  the  interior  of  trees  where  there  is  abun- 

dant moisture  and  deficient  access  of  air,  has  a  different 
composition.  The  water  present  becomes  chemically 
combined,  and  the  product  may  be  regarded  as  differ- 
ing from  the  former,  somewhat  as  a  hydrated  oxide 
differs  from  the  oxide  itself. 


352  ORGANIC    CHEMISTRY. 

8$4.  PREVENTIVES  OF  DECAY.  —  The  ten- 

How  may  the 

decay  of  wood   dency   of  wood  to  decay   is  checked  by 

be  prevented?      ^  and      ^Q     b        certain     salts>        por 


this  purpose,  corrosive  sublimate  and  chloride  of 
zinc  have  been  chiefly  used.  The  process  of  impreg- 
nation with  metallic  salts  is  called  kyanizing. 

885.    INCOMBUSTIBLE     CLOTH.  —  Cotton 

How  is  cloth          IT-  •  T       •  ^     i 

rendered  in-  cloth  immersed  in  a  solution  or  phosphate 
combustible?  Qf  magnesia  js  thereby  rendered  incombus- 
tible. Silicate  of  potassa  is  also  used  on  wood  for  the 
same  purpose. 

886.    EFFECT    OF    SULPHURIC    ACID    ON 

What  is  the 

effect  of  sul-  WOOD.  —  Sulphuric  acid  chars  or  blackens 
Pwood?aCid°n  wood  by  abstracting  a  portion  of  the 
dxygen  and  hydrogen  which  it  contains. 
The  carbon  is  then  left  in  excess,  with  its  characteris- 
tic color.  This  action  of  sulphuric  acid  is  a  conse- 
quence of  its  strong  affinity  for  water,  the  elements 
of  which  it  appropriates  from  most  organic  substances. 
Dilute  sulphuric  acid  has  another  remarkable  effect,  to 
be  hereafter  mentioned. 

887.   EFFECT  OF  NITRIC   ACID.  —  Nitric 

What  is  the  -11,, 

effect  of  nitric  ac  id  gradually  consumes  wood  and  other 
add  on  wood?  organic  matter>  as  effectually  as  if  they 

were  burned  by  fire.  The  final  products  of  its  action 
are  also  the  same  as  those  of  ordinary  combustion. 
This  action  is  accompanied  with  the  evolution  of  orange 
fumes,  as  when  the  same  acid  acts  on  metals.  The 
first  effect  of  nitric  acid  is  to  stain  wood  yellow  ;  for 
which  purpose  it  is  sometimes  employed.  Nitric  acid 
may  also  be  made  to  combine  with  woody  fibre,  form- 
ing gun  cotton. 


WOOD.  353 

What  is  the  888.   EFFECT  OF  MURIATIC  ACID.  —  This 

acid   aci^  has  no  very  striking  effect  on    wood 


on  wood?  or  other  organic  substances.  But  chlorine 
decomposes  and  destroys  them  ;  principally,  in  conse- 
quence of  its  affinity  for  hydrogen,  as  before  explained. 

What  effect  ^89.    EFFECT    OF      ALKALIES.  -  Alkalies 

have  alkalies      have  the  effect  of  hastening  the  decompo- 

on  wood  and  .   . 

similar  sub-  sition  of  organic  substances.  This  effect 
is,  in  part,  due  to  the  fact  that  they  promote 
the  absorption  of  oxygen  from  the  air.  Paper  or  cloth 
in  contact  with  lime  or  potash,  is  found  to  lose  its 
strength  speedily,  and  finally  to  crumble  away.  The 
theory  of  this  action  has  already  been  given  in  the 
paragraph  on  nitrate  of  lime.  Where  the  atmosphere 
is  excluded,  it  would  seem,  from  certain  experiments, 
that  lime  has  an  opposite  effect,  and  rather  retards  than 
promotes  the  decomposition  of  organic  matter. 
What  differ-  890.  W°OD  VINEGAR.  —  The  acid  pro- 

cnt  substances    duct,  as    obtained   in  the  dry    distillation 

are  contained         .  ,        .  ,  .  .  ,  , 

in  wood  vine-  of  wood,  contains,  beside  acetic  acid  and 
gar?  water,  a  sort  of  alcohol,  called  wood- 

spirit,  and  an  oily,  colorless  fluid  called  kreosote.  The 
latter  has  the  odor  of  smoke,  and  has  the  same 
effect  in  preventing  the  putrefaction  of  animal  sub- 
stances. The  effect  of  smoke  is  owing,  indeed,  to  the 
kreosote  which  it  contains.  A  dilute  solution  of  this 
oil  in  water,  is  used  in  medicine  and  for  curing  meats. 
891.  WOOD  TAR.  —  Wood  tar  is  a  mix- 
cl?areSlconan'  ture  of  various  oils,  and  volatile  crystalline 
tained  in  wood  solids  composed  principally  of  carbon  and 
hydrogen.  Kreosote,  which  is  also  ob- 


354 


ORGANIC    CHEMISTRY. 


tained  from  wood  vinegar,  is  one  of  the  oils.  Another 
of  them,  called  eupion,  has  a  pleasant  odor,  somewhat 
similar  to  that  of  the  flower  called  narcissus.  Pittacal, 
a  beautiful  blue  coloring  matter,  resembling  indigo,  and 
paraffine,  resembling  spermacetti,  are  also  obtained  from 
tar. 

892.  COAL  TAR. — Coal  tar 
Jances^r'e        is  produced  from  bituminous 
contained  in     coal,  in  the  process  of  mak- 

coal  tar  ?  ...         . 

ing  illuminating  gas.  It  con- 
sists of  numerous  liquid  and  solid  hydro- 
carbons, produced  by  the  decomposition 
of  the  coal  from  which  it  was  formed. 
Among  them  is  napthaline,  like  camphor 
in  appearance,  and  dissipated,  like  this  sub- 
stance, by  exposure  to  the  air.  Others  are 
mentioned  in  the  next  paragraph.  Coal  tar,  mixed 
with  chalk,  or  other  material,  is  used  as  a  cement,  and 
also  as  a  material  for  covering  roofs. 

893.  USEFUL    PRODUCTS    FROM    COAL 
useful  pro-     '    TAR- — The  first  product  of  its  distillation, 
ducts  of  coal     is  a  light  oil,  commonly  known  as  benzole. 

This  may  be  substituted  for  spirits  of  tur- 
pentine, for  a  great  variety  of  uses.  Another  heavier 
oil,  which  is  obtained  from  it,  is  used  as  a  solvent  of 
india-rubber,  and  also  for  lubrication  and  illumination. 
In  Europe,  the  pitchy  mass,  which  remains  on  dis- 
tillation, is  employed  in  moulding  refuse  coal  dust 
into  cakes,  to  be  used  as  fuel.  The  light  oil  is  also  con- 
verted by  the  action  of  nitric  acid,  into  an  artificial  es- 
sence, similar  to  that  of  bitter  almonds,  used  exten- 


WOOD.  355 

sively  for  scenting  soap.  -Its  vapor,  mixed  with  air,  is 
also  burned  as  gas.  The  heavy  oil  may  be  converted 
by  a  different  action  of  the  same  acid,  into  beautiful 
lemon-colored  crystals  of  carbazotic  acid,  a  substance 
now  used  in  France  as  a  yellow  dye  for  silks  and  wool. 

894.  OILS  FROM  COAL. — The  oils  may 

How  are  oils       ,,';"", 

produced  from  be  directly  produced  from  bituminous  coal 
itself,  and  in  much  larger  quantities  than 
from  tar,  by  avoiding  the  high  temperature  to  which 
coal  is  subjected  in  the  production  of  tar  and  gas. 
The  production  of  oils  by  this  means  promises  to 
be  a  very  important  branch  of  industry. 

895.  GUN-COTTON. — This  material,  so 

How  is  gun- 
cotton  pre-         entirely    harmless   in    appearance,    has    an 

pared?  explosive  energy  superior  to  that  of  gun- 

powder. It  may  be  prepared  by  immersing  ordinary 
cotton,  for  the  space  of  five  minutes,  in  the  strongest 
nitric  acid.  It  is  then  to  be  washed  thoroughly,  and 
dried  at  a  moderate  heat,  for  fear  of  explosion.  The 
material  is  found  to  have  lost  a  certain  portion  of  its 
oxygen  and  hydrogen,  in  the  form  of  water,  and  to 
have  assumed  nitric  acid,  in  its  place.  It  is  not  how- 
ever changed  in  its  appearance.  A  mixture  of  nitric 
acid  with  two-thirds  of  its  volume  of  oil  of  vitriol,  is 
found  to  be  preferable  to  pure  nitric  acid,  in  the  above 
experiment.  The  oil  of  vitriol  assists  in  abstracting 
from  the  cotton  the  water  which  it  is  desired  to  replace 
by  nitric  acid.  Gun-gotton  is  also  called  pyroxyline. 
Similar  compounds,  which  are  less  explosive,  may  be 
prepared  from  sugar  and  starch. 


356  ORGANIC    CHEMISTRY. 

896.  USE  OP  GUN-COTTON, — Gun-cotton. 

What  is  said 

of  Us  proper-  is  not  likely,  for  several  reasons,  to  super- 
cede  gun-powder,  for  use  in  fire-arms.  It 
is  much  more  expensive,  and  so  suddenly  explosive  as 
often  to  burst  the  barrels  in  which  it  is  fired.  Its  ex- 
plosive force  depends,  like  that  of  gun-powder,  on  a 
sudden  combustion  throughout  its  whole  substance, 
and  consequent  evolution  of  a  large  volume  of  mixed 
gases  and  vapor.  Of  these,  carbonic  acid,  nitrogen,  and 
aqueous  vapor  are  the  principal. 

897.  GUN-COTTON  SOLUTION — COLLODI- 

What  in  collo- 
dion ?  How  is  ON. — Gun-cotton  dissolves  in  ether,  form- 
ing a  syrupy  liquid,  which,  on  evapora- 
tion, leaves  behind  a  transparent,  tenacious  film.  It  is 
used,  to  some  extent,  in  place  of  ordinary  court-plaster, 
for  covering  wounds  and  protecting  them  from  the  air. 

HowmayWood  898'    W°°D   CONVERTED  INTO    SUGAR.— 

be  converted  Wood  may  be  converted  into  sugar,  by  caus- 
ing it  to  combine,  chemically,  with  four  ad- 
ditional molecules  of  water.  This  addition  gives  it  the 
precise  composition  and  properties  of  grape  sugar,  and, 
in  fact,  converts  it  into  that  substance.  Poplar  wood  is 
found  best  suited  for  the  purpose,  and  can  be  made  to 
yield  four-fifths  its  weight.  To  effect  the  conversion, 
the  wood  is  first  reduced  to  saw-dust,  then  moistened 
with  somewhat  more  than  its  own  weight  of  oil  of  vit- 
riol, and  left  to  stand  for  twelve  hours.  Being  subse- 
quently pounded  in  a  mortar,  the  nearly  dry  material 
becomes  liquid.  It  is  then  boiled  with  addition  of 
water,  and  the  transformation  is  completed.  It  only 
remains  to  remove  the  sulphuric  acid,  and  evaporate 


STARCH.  357 

the  syrup.  The  former  object  is  effected  by  the  addi- 
tion of  chalk  and  subsequent  nitration,  and  the  latter, 
as  usual,  by  boiling 

TT  899.      WOOD    CONVERTED     INTO    GUM. 

How  is  wood 

converted  into  If  the  boiling  be  omitted  in  the  above  pro- 
cess, the  woody  film  takes  the  form  of  a 
gum,  called  dextrine,  of  the  same  composition  as  the. 
wood  itself,  but  soluble  in  water.  Linen,  or  cotton 
rags,  or  paper,  may  be  converted  into  sugar,  or  gum, 
by  the  same  process.  The  sugar  obtained  is  the  same 
as  that  contained  in  grapes,  and  is  therefore  called 
grape  sugar,  and  also  glucose.  It  differs,  somewhat, 
from  ordinary  cane  sugar,  as  will  be  hereafter  explained. 

STARCH. 

WJiatissaid  ^00.  DESCRIPTION. — Starch  is  identical 

of  the  compo-    in  composition   with  wood  and  gum.     It 

sitlon  and  i          -i          • 

structure  of      consists  of  minute  enveloped  grains,  which 
burst  and  discharge  their  contents    when 
swollen  by  warm  water. 

Where  is  901. — OCCURRENCE. — Starch  isfoiuid 

starch  found?  jn  abundance  in  most  grains  and  other 
seeds ;  in  the  tubers  of  the  potatoe  plant ;  in  many 
fruits,  and  in  the  pith  of  certain  trees.  In  greater  or 
less  quantity,  it  is  contained  in  all  substances  of  vege- 
table origin  which  are  used  as  food.  Horse  chestnuts 
contain  12  per  cent,  of  starch,  and  have  been  used  in 
Europe  for  the  production  of  flour. 

902.    STARCH  FROM  POTATOES. — Starch 

How  is  starch      . 

prepared  from  is  prepared  from  rasped  potatoes,  by  wash- 
potass/  ing  them  Qn  a  seiye>  Th£  water  becomes 


358  ORGANIC    CHEMISTRY. 

% 

milky,  as  it  passes  through,  from  the  fine  starch  grains 
which  it  carries  with  it.  These  are  allowed  to  settle, 
and  being  collected  and  dried,  are  brought  into  com- 
merce as  potatoe  starch.  A  cotton-cloth  may  be  sub- 
stituted for  the  seive  in  this  experiment. 

903.   STARCH  FROM  WHEAT. — If  wheat 

How  is  starch 

made  from,  flour  is  moistened  with  water,  and  exposed 
to  the  air,  it  enters  into  a  putrefaction  which 
destroys,  in  the  course  of  a  few  days,  the 
other  constituents,  and  leaves  the  starch  un- 
affected. The  residue  being  then  washed 
and  dried,  the  manufacture  is  completed.  Io- 
dine may  be  used  as  a  test  for  starch,  as  described  under 
the  head  of  iodides.  Gums  and  woody  fibre,  although 
of  the  same  composition,  are  not  similarly  affected. 

904.      CONVERSION    OF    STARCH    INTO 

How  is  starch  ...  1 

converted  into  SUGAR. — Starch,  like  woody  fibre,  may  be 
converted  into  sugar  through  the  agency 
of  sulphuric  acid.  A  dilute  acid  containing  only  j\  of 
its  volume  of  oil  of  vitriol,  is  brought  to  the  boiling 
point,  and  the  starch  then  added  by  degrees  while  the 
boiling  continues.  A  half  hour  or  a  little  more  suffices 
for  the  conversion.  An  infusion  of  brewer's  malt  has 
the  same  effect  as  the  dilute  acid.  The  sulphuric  acid 
is  then  to  be  removed,  and  the  syrup  concentrated  as 
before  described.  The  sugar  in  this  case  also  is  grape, 
and  not  cane  sugar.  Such  sugar  is  manufactured  largely 
in  Europe  for  adulterating  cane  sugar.  In  England 
its  manufacture  is  prohibited  by  law. 

905.    CONVERSION  OF  STARCH  INTO  GUM. 

How  is  starch      ,-»,--.  ,        ,  • 

transformed      By  keeping  the  liquid  near  to  the  boiling 
into  gum?        point,    without   actual  boiling,  the   gum 


SUGAR.  359 

called  dextrine,  is  obtained  in  the  above  process,  instead 
of  sugar.  It  may  also  be  prepared  by  roasting  starch, 
carefully,  with  constant  stirring,  until  it  acquires  a 
brownish  yellow  color.  This  gum  is  used  largely  in 
calico  printing,  for  thickening  colors.  It  is  also  used  in 
making  the  so-called  "  fig-paste,"  and  certain  other 
kinds  of  confectionery.  The  composition  of  starch 
and  gum  is  precisely  the  same. 

906.   GUM. — Gum  arabic.  and  the  sum 

What  is  said  .  .     .  .          . 

of  natural  of  fruit  trees  generally,  is  identical  in  com- 
gum*l  position  with  woody  fibre  and  starch. 

They  are  either  soluble,  like  gum  arable,  in  water,  or 
swell  up  with  it  to  form  a  thick  paste,  like  gum  traga- 
canth.  The  substance  called  pectine,  which  causes 
the  juice  of  currants,  and  other  fruits  to  stiffen  with 
sugar  into  a  jelly,  is  also  similar  to  the  above  sub- 
stances in  composition.  All  of  these  bodies,  like  wood 
and  starch,  are  convertible  into  sugar  by  the  action  of 
sulphuric  acid. 


SUGAR. 

GRAPE  SUGAR- — The  production 
grape  sugar  of  this  substance  from  wood  and  starch  has 
already  been  described.  It  does  not  exist 
in  the  juice  of  grapes,  as  its  name  would  imply.  The 
sugar  of  the  grape  and  other  acid  fruits,  contains  two 
molecules  less  of  water.  It  is  spontaneously  converted 
into  true  grape  sugar  or  glucose,  and  found  in  incrus* 
tat.ons  upon  the  surface  of  the  dried  fruit.  Those 
fruits  and  trees  which  have  but  little  acid  in  their 


360  ORGANIC    CHEMISTRY. 

juice  or  sap,  commonly  contain  cane  sugar.  The 
sweetness  of  honey  is  due  to  grape  sugar.  This  va- 
riety is  much  Jess  valuable  than  that  of  the  cane,  from 
the  fact  that  it  has  but  little  more  than  one-third  of  its 
sweetening  effect. 

908.  CANE   SUGAR.  —  The  sugar  in  com- 

Whot  is  said  .  .       .  .        '  , 

of  the  compo-    nion  use  is  principally   derived  from  the 
sugar  cane>  an(l  thence  receives  its  distinc- 


trndMt 

artifidal  pro-    tive   name.     It   differs  in  its  composition 

duction  f  f  -i  -i  • 

from  starch,  wood,  and  gum,  in  containing 
a  single  additional  molecule  of  water,  while  grape  sugar 
contains  four.  It  would  seem  from  this  com- 
position, that  it  would  be  more  easily  produced 
by  artificial  means,  from  starch  and  similar 
substances.  But  this  is  not  the  fact.  No 
modification  of  the  process  above  described, 
has  as  yet  been  devised  by  which  starch  and  wood  can 
be  induced  to  take  one  additional  atom  of  water,  in- 
stead of  four.  Such  a  process  would  be  a  discovery 
of  the  greatest  importance,  as  it  would  enable  us  to  con- 
vert our  potatoe  and  grain  fields  at  will,  into  sugar 
plantations,  and  make  us  independent  of  foreign  sup- 
plies. The  figure  represents  a  crystal  of  cane  sugar. 
The  form  belongs  to  the  fourth  system. 

909.     OCCURRENCE.  —  Cane    sugar    is 

What  are  the  .       . 

principal          principally  produced  from  the  sugar  cane, 


from  beets'  and  the  American  maple.  But 
it  is  contained  in  smaller  quantity  in  the 
sap  of  most  plants,  and  in  all  fruits  and  vegetables 
which  are  not  acid  to  the  taste.  The  production  of 
beet  sugar  in  Europe,  in  1850,  was  estimated  at  190,000 


SUGAR.  361 

tons.     That  of  cane  sugar  in  cane  growing   countries 
is  incomparably  greater. 

910.  PRODUCTION. — In  manufacturing 

How  is  cane  ,    . 

sugar  pro-  sugar  from  the  cane,  the  juice  is  first  pressed 
out,  between  heavy  iron  rollers  ;  then  clar- 
ified, and  finally  boiled  down  until  it  will  crystalize  on 
cooling.  The  granular  crystals  form  the  raw  sugar  ; 
the  drainings,  molasses.  Lime  is  the  principal  agent  in 
clarification.  Its  first  effect  is  to  neutralize  the  acid  of 
the  juice,  which,  as  before  seen,  would  gradually  con- 
vert the  cane  sugar  into  grape  sugar,  and  thus  injure 
its  quality.  It  also  precipitates,  with  other  impurities, 
the  gluten,  which,  as  will  be  hereafter  seen,  tends  to 
produce  more  acid.  The  methods  of  producing  sugar 
from  the  beet  and  maple  are  essentially  the  same.  The 
final  purification  of  sugar  by  bone  black  has  already 
been  described. 

911.  MOLASSES. — A  large  portion    of 

How  may  mo-  .  . 

lasses  be  con-     sugar  is  ordinarily  lost  in  the  form  of  mo- 
vertedinto        lasses,  from  which  it   cannot  be  made  to 

sugar  f 

separate  by  crystallization.  This  is  owing 
to  the  presence  of  impurities  not  separated  by  clarifica- 
tion, which  interfere  with  the  process,  in  a  way  not  per- 
fectly understood.  A  method  has  recently  been  con- 
trived of  avoiding  the  loss,  and  thus  largely  increasing 
the  product  of  the  beet  and  cane.  Baryta  added  to  the 
syrup,  combines  with  the  sugar,  and  takes  it  to  the 
bottom  of  the  vessel,  as  a  solid  compound  of  sugar  and 
baryta,  while  the  impurities  remain  behind.  This  pre- 
cipitate is  then  removed  and  diffused  in  water.  Car- 
bonic acid  being  added,  combines  with  the  baryta,  and 

16 


362 


ORGANIC    CHEMISTRY. 


leaves  the  sugar  to  form  a  pure  and  crystallizable  syrup. 
Another  method  of  increasing  the  product  of  sugar  has 
been  described  in  the  section  on  sulphurous  acid. 


How  is  alcohol 

produced  from 


ALCOHOL. 
912.     PRODUCTION    FROM    SUGAR.  —  By 

i  -•  •   • 

the  addition  of  brewers'  yeast  or  some  si- 
milar  ferment  to  sugar,  it  is  gradually  con- 
verted into  alcohol.  Two  molecules  of  water  are  sepa- 
rated in  the  process.  One-third  of  the  carbon  and  two- 
thirds  of  the  oxygen  which  remain,  pass  off  as  carbonic 
acid  gas,  while  alcohol  remains.  The  yeast  enters  into 
no  combination,  and  furnishes  no  material  in  the  pro- 
cess. It  acts  merely  by  its  presence  to  effect  the  de- 
composition, as  will  be  hereafter  explained. 
Explain  the  913.  In  this  process  of  conversion,  each 

diagram.  molecule  of  sugar  makes  two  of  alcohol,  and 
four  of  the  acid.  The  figure  repre- 
sents a  molecule  of  grape  sugar,  after 
the  removal  of  two  molecules  of 
water.  An  arbitrary  arrangement  is 
given  to  the  atoms  for  convenience 
of  illustration.  On  striking  off 
enough  carbon  and  oxygen  from  the 
corners  to  make  the  required  amount 
of  carbonic  acid,  the  residue  may  be  supposed  to  fall 
apart  into  two  molecules  of  alcohol.  Alcohol  is  also 
produced  from  cane  sugar  by  fermentation.  The  first 
stage  in  the  process  is  its  conversion,  by  yeast,  into 


ALCOHOL.  363 

grape  sugar.     The  latter  is  then  changed  into  alcohol 
and  carbonic  acid,  as  above  described. 

914.  COMPOSITION. — The  composition 

What  is  the 

composition  of  of  alcohol  appears  sufficiently  from  the  mid- 
dle groups  of  the  preceding  figure.  Accord- 
ing to  the  theory  of  compound  radicals 
it  is  a  hydrated  oxide  of  ethyle.  The 
principal  group  of  the  annexed  cut, 
represents  a  molecule  of  the  radical  ; 
the  remaining  circles  stand  for  the  oxygen  and  water 
with  which  it  is  combined  in  alcohol. 

915.  PRODUCTION  FROM  POTATOES  AND 

How  is  aico/iol 

made  from  po-     GRAIN. Wliei'6     molasSCS     Or     Solution      of 

sugar  is  the  material  used,  alcohol  is  pro- 
duced as  already  shown.  But  when  potatoes  and  grain 
are  employed  as  the  material,  a  previous  process  is 
necessary  by  which  the  starch  is  converted  into  sugar. 
This  consists  in  the  addition  of  bruised  malt  to  the 
mashed  potatoes  or  grain.  The  diastase  of  the  malt, 
has  the  effect  of  gradually  transforming  starch  into 
sugar  by  its  presence,  as  yeast  converts  sugar  into 
alcohol.  The  mixture  being  kept  at  a  temperature 
of  about  140°,  in  a  few  hours  the  transformation  is 
complete.  The  starchy  mixture  has  become  sweet, 
and  receives  the  name  of  wort.  Brewers'  yeast  and 
water  being  then  added  to  the  wort,  the  conversion  into 
alcohol  commences.  This  is  afterward  separated  from 
the  water  and  refuse  fibre  of  the  potatoe  or  grain  by 
the  process  of  distillation,  described  in  a  subsequent 
paragraph. 


364  ORGANIC     CHEMISTRY. 

What  is  said  916.      PRODUCTION    FROM    ILLUMINATING 

of  the  produc-    GAS — Alcohol  may  also  be  produced  from 

tion  of  alcohol 

from  olefiant  heavy  carburetted  hydrogen,  one  of  the  con- 
gas'  stituents  of  ordinary  illuminating  gas.  This 

is  one  of  the  most  remarkable  results  of  modern  science. 
Most  of  the  processes  of  organic  chemistry  consist  in 
taking  apart  the  complex  molecules  of  organic  matter  and 
reducing  them  to  a  simpler  form,  as  was  illustrated  in  the 
production  of  alcohol  and  carbonic  acid  from  sugar.  Na- 
ture, for  the  most  part,  jealously  withholds  from  man 
the  power  so  to  direct  her  forces  as  to  build  up  arid 
produce  more  complex  organic  substances  by  the  com- 
bination of  those  of  simpler  nature.  This  takes  place 
as  a  general  rule  only  under  the  influence  of  the  vital 
forces  of  vegetable  and  animal  existence,  as  when  the 
plant  produces  sugar  from  the  elements  of  the  atmos- 
phere. The  case  is  an  exception  to  the  general  rule. 
Explain  its  917.  By  reference  to  the  central  group 

production.  of  tne  figure  which  represents  a  molecule 
of  heavy  carburetted  hydrogen,  it  will  be  seen  that  all 
that  is  necessary  to  effect  its  conver- 
sion into  alcohol,  is  the  addition  of 
two  molecules  of  water.  By  long 
agitation  of  the  gas  with  strong  sul- 
phuric  acid,  the  transference  of  part  of  the  water  which 
it  holds  combined  is  effected.  On  subsequent  dilution 
and  distillation,  alcohol  is  obtained  from  the  mixture. 
Carbonate  of  potassa  is  added  in  the  process  of  distil- 
lation, to  diminish  the  proportion  of  water  which  would 
otherwise  pass  off  with  the  alcohol.  After  repeated  dis- 
tillation, strong  alcohol  is  thus  obtained. 


ALCOHOL.  365 

918.  DISTILLATION  OF  ALCOHOL.  —  The 

What  ^,<<  said 

of  fae  presence    process  of  distillation   may  be  illustrated 
of  distillation?    with  the  simple  appals  ^presented  in 


the  figure.  On  heating  wine,  cider  or  beer  in  the  test- 
tube,  its  alcohol  will  be  ex- 
pelled as  vapor  and  re-con- 
densed as  a  colorless  liquid. 
The  cooler  the  vial  is  kept 
the  more  perfect  is  the  condensation.  The  apparatus 
commonly  employed  in  the  distillation  of  alcohol,  con- 
sists of  a  large  copper  vessel  in  which  the  fermented 
wort  is  heated,  and  a  long  tube  called  the  worm,  in 
which  the  vapors  are  condensed.  The  worm  is  made 
to  wind  in  a  spiral,  through  a  tub  of  cold  water,  that 
the  condensation  may  be  more  completely  effected. 
The  spirit  pours  out  at  the  lower  end  of  the  worm, 
where  it  emerges  from  the  tub.  It  may  be  strength- 
ened by  repeated  distillation.  In  order  to  obtain  it 
entirely  free  from  water,  a  highly  rectified  spirit  is 
mixed  with  lime,  or  chloride  of  calcium,  and  re-dis- 
tilled. These  substances  have  such  affinity  for  water, 
that  they  prevent  its  escape  as  vapor,  while  they  in 
no  wise  effect  the  distillation  of  the  alcohol.  By 
this  means  pure  alcohol,  or  absolute  alcohol,  is  ob- 
tained. 

Wimtis  spir-  ^19.     USES    OF    ALCOHOL.  —  Ordinary 

it*  of  wine?      spirits  of  wine  is  a  dilute  alcohol  contain- 

Mention  some     . 

uses  of  aico-      ing  but  about  seventy  per  cent.  01  absolute 
hol?  alcohol.     The    taste   and  odor  of  alcohol 

its  combustible  character,  and  action  as  a  stimulus,  are 
too  familiar  to  need  further  mention.     Its  density,  and 


366  ORGANIC    CHEMISTRY. 

boiling  point,  are  given  in  the  Appendix.  It  is  largely 
used  in  medicine,  and  as  a  solvent  of  oils  and  resins, 
and  many  other  substances  which  water  does  not  dis- 
solve. Medicinal  extracts  of  many  roots  and  herbs, 
"cologne,"  and  other  perfumed  liquids  are  thus  pro- 
duced. 

What  is  the  ^20.    SPIRITUOUS  LIQUORS.  -  SpiritUOUS 

source  of  the     liquors  contain  alcohol  in  large  but  varying 

different  spir-  J 

ituousli-          proportion.      They   differ  in  their  flavor 


according  to  the  material  from  which  they 
are  produced.  Brandy  is  distilled  from  wine,  rum 
from  molasses,  and  whiskey  from  malt  liquors.  The 
latter  name  is  also  given,  in  this  country,  to  the  liquor 
made  from  potatoes,  corn,  and  rye.  In  Europe,  the 
latter  are  more  commonly  called  brandies. 
How  are  wines  921.  WINES.—  Wines  are  produced  by 
produced?  the  fermentation  of  the  juice  of  the  grape. 
On  exposure  to  the  air,  the  gluten  of  the  juice  becomes  a 
ferment,  and  causes  the  conversion  of  the  sugar  into 
alcohol.  The  addition  of  yeast  is  therefore  unneces- 
sary. This  is  also  true  of  the  juice  of  the  apple,  pear, 
and  other  fruits  from  which  fermented  liquors  are  sim- 
ilarly prepared. 

How  is  cham-  922.     CHAMPAGNE.  —  Champagne    and 

pagnemade?  other  sparkling  wines  owe  their  peculiar- 
ity to  the  presence  of  carbonic  acid,  in  large  propor- 
tion. This  is  secured  by  allowing  the  last  stages  of 
fermentation  to  proceed  in  firmly  corked  bottles,  so 
that  all  the  gas  which  is  evolved  is  retained.  Or  an  or- 
nary  wine  is  first  produced  by  the  usual  process,  and 
sugar  and  yeast  are  then  added,  to  excite  a  new  fer- 
mentation in  the  bottled  liquid. 


MALT    LIQUORS.  367 

What  is  said  ^23.  ALCOHOL  IN  WINES.  —  Wines  differ 


of  the  pro-        in  the  amount  of  alcohol  which  they 

portion  of  al-          . 

coholin  tain;  from  five  per  cent.,  in  the  weakest 

champagne,  to  twenty-five,  in  the  strongest 
sherry.  Those  of  southern  climates  are  strongest,  be- 
cause the  grapes  of  those  regions  contain  more  sugar 
to  undergo  conversion  into  alcohol.  Most  wines  also 
contain  more  or  less  acid  and  urifermented  sugar. 
What  is  said  924.  TARTAR.  —  The  acid  of  wine  is 

of  acid  in  .  .,          ,  .    .  .  ^  .  . 

\tines?  tartanc  acid,    which    exists    in    combina- 

tion with  potash  in  the  juice  of  the  grape.  It  grad- 
ually deposits  in  wine  casks  in  the  form  of  acid  tar- 
tra'te  of  potash  or  cream  of  tartar.  This  separaton 
of  tartar  is  one  source  of  the  improvement  of  wines, 
and  more  particularly  of  the  rhenish  wines,  by  age. 

925.     FLAVOR  OF    WINES.  —  The  wine 

What  is  said  . 

of  the  flavors  flavor  which  belongs  to  all  wines,  is 
owing  to  the  presence,  in  extremely  small 
portion,  of  an  etherial  liquid  called  aenanthic  ether. 
Tliis  substance  does  not  exist  ready  formed  in  the 
grape,  but  is  produced  in  the  re-arrangement  of  atoms 
which  takes  place  in  fermentation.  Its  vinous  odor, 
when  separated  from  the  wine,  is  most  intense.  It  is 
prepared  in  Europe  from  grain  spirit  or  cheap  wines, 
and  is  used  in  this  and  other  countries  for  producing  imi- 
tations of  wines  of  higher  price.  Potatoe  whiskey  is 
commonly  the  basis  of  these  manufactured  wines. 
Beside  the  general  vinous  flavor,  different  wines,  like 
flowers,  have  an  aroma,  or  bouquet,  peculiar  to  them- 
selves. These  are  owing,  to  other  and  different  flavor- 
ing substances,  present  in  still  smaller  proportion,  than 
the  aenanthic  ether. 


368  ORGANIC    CHEMISTRY. 

926.   BEER  AND  ALE. — Beer  is  the  fer- 

tfow  are  malt 

liquors  pre-  merited  extract  of  malted  grain.  The  malt 
pare  '  is  prepared  by  softening  barley  in  water, 

and  then  allowing  it  to  sprout  or  germinate.  Diastase, 
which  is  formed  in  the  process  of  germination,  con- 
verts the  starch  of  the  grain  into  sugar,  and  thus  pre- 
pares it  for  the  subsequent  process  of  fermentation. 
Yeast  and  hops  are  added  to  the  extract  of  malt,  which 
is  called  the  wort,  to  bring  about  fermentation  and 
help  to  give  the  product  flavor.  Ale  is  a  similar  malt 
liquor  of  different  color.  Porter  is  a  darker  variety  of 
beer,  made  from  malt  which  has  been  browned  by 
roasting. 

927.  CONVERSION    OF    ALCOHOL    INTO 

How  is  alcohol  .  ,      ,     ,     .  ,     . 

converted  into  ETHER. — Alcohol  is  converted  into  ether 
ether  ?  ky  heating  witn  o{\  of  vitriol.  To  illus- 

trate its  preparation,  equal 
volumes  of  strong  alcohol 
and  oil  of  vitriol  may  be 
thoroughly  mixed  in  a  test- 
tube,  and  the  vapors  con- 
densed in  a  cool  vial,  as  J 
represented  in  the  figure. 
A  little  sand  may  be  added  to  the  mixture  with  advant- 
age. The  vial  should  be  kept  cool  by  means  of  paper 
repeatedly  moistened,  during  the  process.  The  space 
between  the  tube  and  the  neck  of  the  vial  should  also 
be  loosely  closed  with  wet  paper. 

928.  EXPLANATION. — Alcohol    is,    as 

Explain  the  -,*••/• 

above  re-ac-       above  stated,  the  hydrate   of  the  oxide  of 
tl011'  ethyl.     Sulphuric  acid  combines  with  tho 


ETHYL.  369 

oxide  itself,  on  heating,  forming  a  bi- 
sulphate,  and  at  a  little  higher  tem- 
perature, yields  it  up  again,  as  gaseous 
ether  or  oxide  of  ethyl.  The  change 
in  the  alcohol  consists,  simply,  in  the  loss  of  an  atom 
of  water.  The  whole  figure  represents  a  molecule  of 
alcohol ;  the  lower  portion  one  of  ether. 

929.  PRODUCTION    OF    ETHYL. — The 

How  is  the  -i  •      i        11 

radical  ethyl  radical  ethyl  cannot,  like  many  metals,  be 
procured?  directly  produced  from  its  oxide.  Heat, 
or  other  means,  applied  to  accomplish  this  object, 
destroys  the  radical  itself.  But  the  end  may  be 
reached  by  a  circuitous  process.  This  consists  in  first 
producing  from  the  oxide,  an  iodide 
of  ethyl,  and  then  removing  the  iodine 
by  a  metal.  A  colorless  gas,  of  the 
composition  indicated  by  the  hydrogen  and  carbon  at- 
oms of  the  figure,  is  thus  evolved. 

930.  CONVERSION   OF    ALCOHOL    INTO 

How  is  alcohol 

convertedinto       OLEFIANT  GAS. The     production     of    alcO- 

olefiantgas?       ^    fr()m    olefiant  gag    hag    been    described 

in  the  section  on  hydrogen.  The  subject  is  again  in- 
troduced, for  the  purpose  of  illustrating  the  change,  by 
reference  to  the  atomic  composition  of  the  two  sub- 
stances. Representing  the  atom  of 
alcohol  as  before,  it  is  converted  by 
the  removal  of  two  atoms  of  oxy- 
gen, and  two  of  hydrogen,  into  olefi- 
ant gas.  The  composition  of  this  gas  is  indicated  by 
the  central  group  of  the  annexed  figure.  The  ab- 
straction of  oxygen  and  hydrogen  is  effected  through 
16* 


370  ORGANIC    CHEMISTRY. 

the  agency  of  the  sulphuric  acid  used  in  the  process. 
It  will  be  observed  that  the  radical  ethyl,  which  has  re- 
mained permanent  in  the  changes  before  described,  is 
here  destroyed,  by  the  abstraction  of  a  part  of  its  hy- 
drogen. 

What  is  aide-  931.   CONVERSION  OF  ALCOHOL  INTO  ALDE- 

hyde?  HYDE. — Aldehyde  is  a  clear  colorless  liquid 

of  a  peculiar  ethereal  odor,  produced  by  the  action  of 
the  air  or  oxygen  on  alcohol.  It  is  the  product  of  a 
partial,  slow  combustion,  or  ereme- 
causis  of  the  alcohol,  and  forms  the 
middle  point  in  the  conversion  of 
alcohol  into  vinegar.  It  is  for  this 
reason  that  it  is  here  introduced. 

932.     The    two   atoms  of  hydrogen, 

How  is  alcohol        ,  .   ..  ,  ,  . 

converted  into  which  are  burned  out  m  the  process,  are 
aldehyde  ?  indicated  in  the  figure  by  smaller  inscribed 
letters.  By  the  removal,  the  radical  ethyl  is  converted 
into  the  radical  acetyl.  Aldehyde  is  therefore  a  hy- 
drated  oxide  of  acetyl.  The  characteristic  odor  of  the 
substance  is  often  perceived,  in  the  process  for  making 
vinegar.  It  may  also  be  produced  by  depressing  a  wire 
gauze  upon  an  alcohol  flame,  and  thereby  making  the 
combustion  incomplete. 

933.  CONVERSION  OF  ALCOHOL  INTO  VIN- 

ZSZZ&f  »»«— If  dll«te  alcoho1  ;s  exposed  to  the 
alcohol  into  air?  it  is  converted,  by  oxidation,  into  ace- 
tic acid.  Part  of  its  hydrogen  having  been 
burned  out  to  form  aldehyde,  the  oxy- 
gen acts  further  to  oxidize  the  alde- 
hyde which  has  been  produced.  The 
composition  of  each  molecule  is  such 


VINEGAR.  371 

as  is  represented  in  the  preceding  figure.  It  will  be  ob- 
served that  the  oxygen  added  is  just  sufficient  to  sup- 
ply the  place  of  the  hydrogen  removed  in  the  formation 
of  aldehyde.  The  latter  substance  being  a  hydrate  of 
the  protoxide  of  acetyl,  acetic  acid  is  a  hydrated  terox- 
ide  of  the  same  radical.  The  presence  of  yeast  or 
some  other  similar  ferment,  is  essential  in  the  produc- 
tion of  vinegar,  as  well  as  in  that  of  alcohol. 

Describe  the  934.       PROCESS      OF      MANUFACTURE. A 

process.  few  years   since,  vinegar  was  exclusively 

produced  by  the  souring  of  .wine  or  cider.  At  pres- 
ent, large  quantities  are  made  from  alcohol,  by  diluting 
it  with  water,  adding  a  little  yeast,  and  then  exposing 
it  to  the  action  of  the  air.  This  is  best  accomplished 
by  allowing  the  diluted  alcohol  to  trickle  through  shav- 
ings, packed  in  well  ventilated  casks.  A  few  passages 
through  the  cask  suffices  to  convert  the  liquid  into 
vinegar.  The  addition  of  yeast  is  unnecessary  in  pro- 
ducing vinegar  from  cider  or  wine,  as  these  liquids  con- 
tain a  substance  which  acts  as  a  ferment.  The  vapor 
of  alcohol  may  be  readily  converted  into  acetic  acid 
by  contact  with  platinum  black.  The  property  of  pla- 
tinum to  produce  oxidation  in  similar  cases,  has  been 
already  explained. 

935.  CHLOROFORM. — Chloroform  is  best 

Howischloro-  .  ...... 

formprepar-     obtained   by  distilling  pure   alcohol   with 

water  and  bleaching  powder.  Its  mole- 
cule consists  of  two  atoms  of  carbon,  and 
one  of  hydrogen,  combined  with  three  of  chlorine.  The 
carbon  and  hydrogen  atoms  are  regarded  as  more  inti- 
mately combined  to  form  the  radical  formyl.  Chloro- 


372  ORGANIC    CHEMISTRY. 

form  is  therefore  a  terchloride  of  this  radical.  It  is 
a  colorless  and  volatile  liquid,  of  a  peculiar,  sweetish 
smell.  The  inhalation  of  its  vapor,  produces  insensi- 
bility to  pain,  and  is  much  employed  in  surgical  ope- 
rations, for  this  purpose.  Ether  has  the  same  effect, 
in  a  less  degree.  A  mixture  of  the  two,  is  more  com- 
monly employed  in  this  country. 

936.   FUSEL  OIL. — Fusel  oil  is  a  peculiar 

What  is  fusel     ,.,-.,,         f  . 

oil?  Mention  kind  of  alcohol,  of  extremely  nauseous 
its  properties.  Q^  an(j  pOjsonous  properties,  which  ac- 
companies ordinary  alcohol  in  its  production  from 
potatoes  and  grain.  It  may  he  separated  by  nitration 
through  charcoal.  But  this  process  of  purification  is 
often  neglected,  and  the  fusel  oil  left  to  add  its  poison 
to  the  deleterious  effects  of  the  alcohol  itself.  It  is 
this  doubly  poisonous  alcohol  which  forms  the  basis 
of  numerous  manufactured  liquors,  wines,  and  cordials. 
Fusel  oil  is  the  hydrated  oxide  of  amyl.  This  radical 
contains  ten  atoms  of  carbon,  to  eleven  of  hydrogen. 
It  belongs  to  the  series  of  alcohols  mentioned  in  the 
first  chapter  of  organic  chemistry. 

ORGANIC  ACIDS. 

mat  is  said  937-  ACETIC  ACID.— Ordinary  vinegar 
of  theproduc-  js  a  dilute  acetic  acid.  It  cannot  be  con- 

tion  and  prop- 
erties of  acetic    centrated   by   evaporation,   as   the  acid    is 

volatile,  as  well  as  the  water  which  dilutes 
it.  To  obtain  the  strong  acid,  recourse  is  had  to  the 
salts  of  acetic  acid,  from  which  it  is  prepared  by  the 
method  used  for  nitric  and  muriatic  acids.  The  pure 


TANN1C    ACID.  373 

acid  is  a  solid.  It  mixes  with  water  at  low  tempera- 
ture, in  all  proportions,  and  is  commonly  seen  in  its  dis- 
solved state.  Its  compounds  with  metallic  oxides  are 
called  acetates.  The  sugar  of  lead,  so  called,  is  an 
acetate,  formed  by  dissolving  litharge  in  acetic  acid. 

938.   TANNIC  ACID.  —  Tannin,  or  tannic 
e      acid>   exists  in  nut-galls    and  in  the  bark 


properties  of     and  leaves  of  many  trees.     It  is  the  prin- 

tannic  acid  ?          .    .          ....  .  ,     . 

ciple  which  imparts  to  them  their  astrin- 
gent taste,  and  gives  to  the  tan  liquor  the  property  of 
converting  hides  into  leather.  When  separated  from 
the  other  substances  with  which  it  is  combined  in 
nature,  it  is  a  yellowish,  gummy  mass.  It  is  soluble  in 
water,  and  possesses  the  property  of  precipitating  glue 
or  gelatin,  and  many  other  metallic  oxides. 

939.  WRITING   INK.  —  Common   writing 

What  is  the  . 

coloring  mat-     ink  is  prepared  from  nut-galls  and  proto- 
ter^of  writing    sulphate  of  iron>     When  first  made,  it  is 

principally  a  tannate  of  the  protoxide  of 
iron,  and  forms  a  very  pale  solution.  Before 
it  is  fit  for  use,  it  must  be  exposed  for  a  time 
to  the  air,  and  thereby  converted,  partially,  into 
tannate  of  the  peroxide.  This  is  a  bluish  black 
precipitate,  and  imparts  to  it  the  requisite  color. 
It  is  essential  to  the  permanence  of  ink,  that 
the  change  should  take  place,  in  part,  in  the  fibre  of 
the  paper  itself.  Too  long  exposure  should,  therefore, 
be  avoided  in  the  manufacture.  The  pale  ink  thus 
produced,  which  blackens  further  in  using,  is  much  more 
permanent  than  a  thicker,  darker  ink,  produced  when 
this  caution  is  not  observed. 


374  ORGANIC    CHEMISTRY. 

940.  Six  parts  of  nut-galls  to  four  of 

Give  the  pro- 

cess of  its          copperas,  are  found  to  be  the  best  propor- 

preparation.      tiong  for  prO(}Ucing  a  permanent  ink.     The 

galls  are  to  be  boiled  with  water,  the  decoction  strained, 
and  mixed  with  copperas  solution.  Gum  and  cloves 
are  added,  the  former  to  keep  the  coloring  matter  of  the 
ink  from  settling,  and  the  latter  to  prevent  its  moulding. 
After  a  ripening  of  a  month  or  more  the  liquid  is 
strained.  The  coloring  matter  of  ink  is  immediately 
produced  in  a  solution  of  copperas,  as  a  bulky  precipi- 
tate, by  the  addition  of  tincture  of  galls,  and  a  little 
nitric  acid. 

HYDROCYANIC  ACID. 
941.     CYANOGEN.  —  Before     proceeding 

Mention  the  .  . 

composition       with   the  description    of   hydrocyanic,   or 


Pmssic  acid>  the  production  of  cyanogen, 

which  enters  into  its 
composition,  will  be  briefly  consid- 
ered. Cyanogen  is  a  colorless  gas, 
with  a  peculiar  odor,  resembling 
that  of  peach  pits.  It  is  nearly  twice 
as  heavy  as  atmospheric  air.  It 
burns  with  a  beautiful  purple  flame. 
Cyanogen  is  a  compound  radical, 
posssessed  of  important  analogies  to 
chlorine,  and  the  other  electro-neg- 
ative elements.  Its  molecule  contains  one  atom  of  ni- 
trogen and  two  of  carbon. 

How  is  cyano-        942.  PRODUCTION.  —  Cyanogen  may  be 
gen  prepared?   expelled  from  the  cyanide  of  mercury,  by 


CYANIDES.  375 

the  agency  of  heat.  This  metal  retains  cyanogen  as 
it  does  oxygen,  but  feebly.  A  method  more  commonly 
employed  is  to  produce  and  decompose  the  cyanide  of 
mercury  at  the  same  moment.  This  is  effected  by 
mixing  chloride  of  mercury,  to  furnish  the  metal,  with 
the  double  cyanide  of  iron  and  potassium,  which  fur- 
nishes the  cyanogen.  The  other  elements  unite  to 
form  chlorides  of  iron  and  potassium,  while  the  cyanide 
of  mercury  is  decomposed  as  fast  as  it  is  formed.  The 
double  cyanide  of  iron  and  potassium,  above  referred  to, 
is  the  commercial  yellow  prussiate  of  potash.  Two  parts 
of  this  salt  are  to  be  heated  with  one  of  bi-chloride  of 
mercury,  in  the  above  process.  The  prussiate  cannot 
be  used  alone  for  the  production  of  cyanogen,  on  ac- 
count of  the  firm  retention  of  this  radical  by  the 
highly  electro-positive  metals  which  enter  into  the  com- 
position of  the  salt. 

How  isc  a-  ^^*  CYANIDE   OF  POTASSIUM. — Cyanide 

nide  of  potas-    of  potassium  is  a  white  substance,  resem- 

siumprepar-       ,  ..  ...  , 

ed?  Mention  bling  porcelain  m  appearance,  and  quite 
soluble  in  water  arid  Alcohol.  It  is  largely 
employed  in  preparing  solutions  of  the  precious  metals, 
for  galvanic  gilding  and  silvering.  It  is  produced  on  a 
large  scale,  by  fusing  together  carbonate  of  potash  and 
refuse  animal  matter.  The  latter  furnishes  the  carbon 
and  nitrogen  required  for  the  production  of  cyangen, 
while  the  carbonic  acid  and  oxygen  of  the  salt,  are 
principally  evolved  as  oxide  of  carbon.  The  cyanide 
of  potassium  is  best  extracted  from  this  residue  by  alco- 
hol, which  leaves  the  other  material  undissolved. 


ORGANIC    CHEMISTRY. 


376 


How  is  yellow         944    P^ssiATE   OF  POTASH.—  Cyanide 

prussiate  of  of  iron  is  always  incidentally  formed  from 

potash  pre-  . 

pared?  Men-  the  iron  of  the  vessel  in  the  above  process. 

tion  its  uses,  jf  Wftter  ig  added    t()  th 


cyanides  dissolve  ;  although  the  latter,  when  alone,  is 
entirely  insoluble.  From  the  solution,  the  double  cy- 
anide of  potassium  and  iron,  mentioned  in  a  preceding 
paragraph,  is  obtained,  by  evaporation,  in  splendid  yel- 
low crystals.  It  is  known  in  commerce  as  yellow 
prussiate  of  potash,  and  is  largely  used  in  the  arts  for 
the  production  of  prussian  blue  and  cyanide  of  potas- 
sium. Prussian  blue  is  obtained  by  adding  its  solution 
to  a  salt  of  the  peroxide  of  iron.  As  any  solution  of 
iron  is  readily  peroxydized  by  the  addition  of  a  little 
nitric  acid,  the  yellow  prussiate  may  be  employed  as  a 
test  for  this  metal. 

945.     FERROCYANIDES.  —  The     yellow 

What  is  said  3 

of  ferrocya.no-  prussiate  of  potash,  produced  as  above  de- 
scribed, is  not  properly  a  double  cyanide 
of  iron  and  potassium.  There  is  reason  to  believe 
that  the  cyanogen  is  more  intimately  combined  with 
the  iron  than  such  a  name  would  imply.  It  seems  to 
have  lost  its  ordinary  properties,  in  the  compound. 
Neither  the  alkalies,  or  sulphide  of  ammonium,  which 
usually  precipitate  iron  from  its  solutions,  have  any 
power  to  precipitate  it  from  this  salt.  The  three  mole- 
cules of  cyanogen,  which  enter  into  its  composition, 
seem  to  have  hidden  and  absorbed  it.  They  have 
formed  with  it,  indeed,  a  new  compound  radical,  called 
ferrocyanogen.  The  double  salt  above  mentioned  is 
therefore  more  properly  a  ferrocyanide  of  potassium. 


PRUSSIC    ACID.  377 

Ferrocyanogen,  like  all  other  compound  radicals,  con- 
ducts itself,  under  ordinary  circumstances,  as  an  ele- 
mentary substance. 

WJiatisfcrri-  946.  On  tne  removal  of  one  atom  of 
cyanogen?  potassium  from  two  molecules  of  this  salt, 
a  coalescence  of  the  ferrocyanogen  of  the  two  mole- 
cules seems  to  be  the  result,  and  a  new  compound  radi- 
cal is  formed.  This  radical  is  called  ferricyanogen. 
It  combines  with  the  three  remaining  atoms  of  potas- 
sium, to  form  ferricyanide  of  potassium. 
Give  the  ro  -  ^^ '  PRUSSIC  ACID. — Hydrocyanic  acid 
erties  of  prus-  is  made  from  cyanide  of  potassium,  by  the 
its  mode  of  same  method  employed  for  producing  hy- 
preparation.  drochloric  acid  from  common  salt.  The 

ferrocyanide  of  potassium  is  more  commonly  employed 
in  the  process.  Prussic  acid  is  intensely  poisonous.  A 
drop  or  two  of  the  concentrated  liquid,  placed  upon  the 
tongue  of  a  dog,  produces  immediate  death.  On  ac- 
count of  its  extremely  dangerous  properties,  the  prepa- 
ration of  the  acid  should  never  be  attempted  except 
by  a  professional  chemist.  The  odor  of  the  acid  is 
somewhat  similar  to  that  of  cyanogen,  and  may  be  fre- 
quently detected  in  the  vicinity  of  establishments  where 
galvanic  gilding  is  conducted.  Ferrocyanogen  and  fer- 
ricyanogen, like  simple  cyanogen,  have  their  hydrogen 
acids  and  series  of  salts.  The  acid  of  the  former  is 
bibasic,  and  that  of  the  latter  tribasic,  as  already  shown 
by  the  composition  of  their  potassium  compounds. 
What  is  said  ^48.  OTHER  ORGANIC  ACIDS. — Tartaric 
of  citric, ma-  acid,  before  mentioned,  is  found  in  the 

lie,  lactic,  ox- 
alic, and  for-     grape.       The   acid   tartrate  of  potassa    or 

mie  acids  ?        cream  of  tartar,  which  deposits  in  wine 


378  ORGANIC    CHEMISTRY. 

casks,  is  one  of  its  most  important  salts.  Another  has 
been  mentioned  under  the  head  of  antimony.  Oxalic 
acid  is  found  in  wood  sorrel  and  in  certain  lichens.  It 
is  also  prepared  by  the  action  of  nitric  acid  on  wood, 
sugar,  and  starch.  When  these  substances  are  burned 
in  the  air,  their  carbon  is  converted  into  carbonic  acid. 
Oxalic  acid  contains  half  the  proportional  quantity  of 
oxygen,  and  may  be  regarded  as  the  product  of  a  less 
perfect  combustion  by  the  oxygen  of  nitric  acid.  It  is 
a  white  crystalline  solid  and  a  most  dangerous  poison. 
The  effect  of  heat  on  oxalic  acid,  with  its  precise  com- 
position, is  given  in  the  section  on  carbonic  oxide. 
Citric  acid  is  the  acid  of  lemons,  malic  acid,  that  of 
the  apple,  and  formic  acid  that  of  the  red  ant.  The 
latter  may  also  be  formed  from  wood  spirit,  by  oxida- 
tion, through  the  agency  of  platinum  black,  as  acetic 
acid  is  formed  from  ordinary  spirit  or  alcohol.  Lactic 
acid  will  be  again  mentioned  under  the  head  of  animal 
chemistry. 

949.   THEIR  COMPOSITION. — All  of  these 

What  is  the 

composition  of  acids  differ  in  taste  and  in  various  chem- 
*acids?Ve  *ca^  Pr°Perties?  as  do  those  of  inorganic 
chemistry.  Yet  all  of  them  contain  the 
same  three  elements  which  are  also  contained  in  wood, 
gum,  and  starch.  They  contain  these  elements  in 
various  proportion,  but  their  peculiarities  are  not  to  be 
ascribed  to  this  cause  alone.  They  may  be  regarded 
as  in  part,  at  least,  the  consequence  of  a  difference  of 
arrangement  of  the  atoms,  as  has  already  been  ex- 
plained 


ESSENTIAL    OILS.                                        379 
ESSENTIAL  OILS. 
What  is  said  ^50.      V°LATILE,     OR    ESSENTIAL    OILS. • 

of  the  compa-    Oils  of  turpentine  and  lemon,  and  otto  of 

rative  compo- 
sition of  es-       roses,  are  examples  of  essential  oils.     They 
sential  oils  ?     are  aimost  as  various  as  plants  themselves. 

Yet  the  composition  of  those  that  differ  most  widely 
is  often  the  same.  This  is  the  case  with  the  oils  of 
orange,  lemon,  pepper,  turpentine,  juniper,  parsley, 
citron  and  bergamot.  They  contain  carbon  and  hy- 
drogen alone,  and  in  the  same  proportion;  twenty 
atoms  of  the  former  to  eight  of  the  latter.  Those  of 
bitter  almonds,  cinnamon,  cloves,  and  anise-seed,  con- 
tain oxygen  beside.  Those  of  mustard,  and  onions, 
contain  oxygen,  and  sulphur,  in  addition,  and  are  char- 
acterized, like  all  sulphuretted  oils,  by  a  peculiar,  pun- 
gent smell,  and  acrid,  burning  taste. 

951.   OCCURRENCE    AND  PREPARATION. — 

How  are  the  . 

essential  oils  Essentials  oils  are  oftenest  found  in  the 
prepared?  flowers,  seeds,  and  fruits  of  plants,  but 
sometimes  in  the  stalks  and  roots.  From  these  they 
are  obtained  by  distillation  with  water.  The  volatile 
oil  passes  over  with  the  steam,  and  floats  upon  the  con- 
densed liquid  in  the  receiver.  Oil  of  turpentine  is  thus 
made,  from  the  common  turpentine,  or  pitch  as  it  is 
sometimes  called,  which  exudes  from  the  pine  ;  ordi- 
nary rosin  remains  behind.  The  delicate  perfume  of 
violets,  and  other  flowers  which  contain  but  a  small 
portion  of  essential  oil,  is  extracted  by  mingling  the 
flowers  with  lard.  This  substance  has  the  property  of 
absorbing  the  oil,  and  yielding  it  again  by  distillation. 


co 


380  ORGANIC    CHEMISTRY. 

952.      USE     OF     THE      ESSENTIAL     OILS.  - 

What  are  the  .  . 

uses  of  the  es-  1  he  essential  oils  are  extensively  em- 
senttal  oils  ?  ployed  in  the  manufacture  of  essences,  per- 
fumes, and  cordials.  All  of  these  liquids  are  solutions 
of  the  oils  in  alcohol,  with  the  addition,  in  the  case  of 
cordials,  of  a  portion  of  sugar.  The  oil  of  turpentine 
is  used  in  the  manufacture  of  varnishes  and  burning 
fluid,  to  be  hereafter  described. 

953.  BURNING  FLUID.  —  "  Burning  fluid," 

What  is  the 

position  of  so  called,  is  a  solution  of  camphene  or 
rectified  turpentine  in  alcohol.  The  sole 
object  of  the  camphene  is  to  increase  the 
proportion  of  carbon,  and  thus  render  the  flame  more 
luminous.  Unmixed  camphene  may  also  be  burned  in 
lamps  provided  with  tall  chimneys.  The  effect  of  the 
chimney  is  to  make  a  strong  draft,  and  thus  provide  a 
liberal  supply  of  oxygen  in  proportion  to  the  large 
amount  of  carbon  which  the  liquid  contains.  With- 
out this  provision,  camphene  burns  like  camphor,  with 
much  smoke,  depositing  a  large  part  of  its  carbon  in 
the  form  of  soot  or  lamp-black. 

What  is  said  954  BURNING  FLUID,  "EXPLOSIVE."— 
of  the  expio-  The  mixture  of  alcohol  and  camphene, 

sibility  of  ./,.-,•  i 

"  burning-  known  as  burning  fluid,  is  commonly 
spoken  of  as  explosive.  That  this  is  not 
the  fact,  may  be  readily  shown  by  pouring  a  little  in  a 
saucer,  and  inflaming  it.  It  burns,  under  these 
circumstances,  as  quietly  as  from  the  wick  of  a 
lamp.  But  if  a  can,  containing  burning  fluid,  be 
shaken  up  and  then  emptied  of  its  liquid  con- 
tents, it  is  found  to  contain  an  explosive  atmos- 
phere. To  prove  this,  it  may  be  tightly  corked 


BURNING    FLUID.  381 

and  fired  through  a  small  hole  punched  in  the  side.  On 
applying  a  lighted  taper  to  the  opening,  the  can  explodes 
with  a  loud  report,  and  is  torn  to  pieces  by  the  force 
of  the  escaping  gases.  The  small  proportion  of  fluid 
remaining  in  the  can,  after  every  drop  that  can  be 
poured  out  is  removed,  is  sufficient  to  produce  this 
effect. 

955.  EXPLANATION. — The  principle   of 

What  is  the 

cause  of  the  the  explosion  is  precisely  the  same  as  that 
explosion?  involved  in  the  same  experiment  with  hy- 
drogen and  air.  The  only  variation  consists  in  the  sub- 
stitution of  the  combustible  vapor  of  alcohol  and  cam- 
phene,  for  hydrogen  gas.  It  is  the  mixture  of  alcohol 
vapor,  and  air,  to  which  the  effect  is  to  be  principally 
ascribed  ;  the  experiment  may  be  made,  indeed,  as 
well  with  unmixed  alcohol,  or  ether,  as  with  burning- 
fluid.  It  may  also  be  made  with  camphene,  but  in  this 
case  the  vessel  must  be  warmed,  in  order  to  vaporize 
the  liquid  in  sufficient  quantity. 

956.  The    above    experiment   may    be 

Describe  an-  /.  j        •.-,         c  ,  •    i     -u 

other  form  of  performed  with  safety,  in  an  open  vial,  by 
the  expert-  vaporizing  a  drop  or  two  of  either  of  the 
above  liquids  within  it,  and  then  apply- 
ing a  lighted  taper  to  the  mouth.  In  this  case,  the  ap- 
pearance of  flame  at  the  mouth  of  the  vial,  and  a 
rushing  noise,  is  all  that  is  observed.  This  experiment 
will  enable  the  student  to  disprove  the  alleged  unex- 
plosive  character  of  certain  fluids  in  use  for  purposes 
of  illumination.  In  moderately  warm  weather  it  is 
sufficient  to  fill  the  vial,  and  then  to  empty  it,  in  order 
to  form  the  explosive  atmosphere. 


382  ORGANIC    CHEMISTRY. 

957.   ARTIFICIAL    ESSENCES. — Many    of 

What  «*  naid 

of  artificial  the  essentials  oils  are  compounds  of  organic 
acids  and  bases.  Several  of  them  may  be 
artificially  produced.  Pine  apple  oil  is  a  compound 
butyric  acid  with  ether  or  oxide  of  ethyl.  The  bu- 
tyric acid  of  the  compound  may  be  prepared  from 
rancid  butter  or  by  fermenting  sugar  with  putrid 
cheese.  Bergamit  pear  oil  is  an  alcoholic  solution  of 
acetates  of  the  oxide  of  ethyl,  with  acetate  of  oxide 
of  amyl.  The  latter  is  the  ether  of  the  nauseous  and 
poisonous  fusel  oil,  which  has  before  been  mentioned. 
What  is  arti-  958.  Apple  oil  is  a  compound  of  vale- 
fdal  apple  rianic  acid  with  the  same  ether.  The 

oil?     Artifi- 
cial oil  of  bit-    valenanic    acid    of  the  compound    is    also 
ter  almonds?     ^^  from  fugel  Q^      Oil  of  grapes,  and 

oil  of  cognac,  used  to  impart  the  flavor  of  French 
brandy  to  common  alcohol,  come  from  the  same  source. 
Oil  of  winter-green  may  be  prepared  from  willow  bark 
and  wood  vinegar.  Oil  of  bitter  almonds  is  prepared 
from  coal  tar.  These  artifical  essences,  although  pro- 
duced in  several  cases  from  poisonous  substances,  may 
be  used  as  flavors  with  perfect  safety.  It  is  highly 
probable  and  in  many  cases  certain,  that  the  flavor  of 
the  fruits  themselves,  is  owing  to  the  presence  of  these 
precise  compounds,  in  small  quantities. 
,jr,  ,  959.  EMPYREUMATIC  OILS. — The  vola- 

What  are  em- 

pyreumatic  tile  oils  which  are  produced  by  the  de- 
structive distillation  of  vegetable  and  ani- 
mal substances  receive  this  general  name.  The  oils 
of  wood  and  coal  tar  are  examples.  Another  em- 
pyreumatic  oil  is  produced  in  the  combustion  of  to- 


RESINS.  383 

bacco  in  ordinary  pipes.  This  oil  is  extremely  poison- 
ous. It  is  to  be  understood  that  these  oils  do  not  exist 
ready  formed  in  the  substances  from  which  they  are 
obtained,  but  are  produced  in  the  re-arrangement  of 
atoms,  which  takes  place  when  organic  bodies  are  sub- 
jected to  a  high  temperature. 

960.   CAMPHORS. — Several  of  the  oxy- 

What  is  the  .  J 

origin  of  the  genated  essential  oils  deposit  white  crystal- 
wnphonf  line  solids  by  cold  These  are  frequently 

isomeric  with  the  oils  themselves,  and  are  called  cam- 
phors. Ordinary  gum  camphor  is  obtained  like  the  es- 
sential oils,  by  the  distillation  of  the  leaves  of  the  Lau- 
rus  Camphor  i  with  water.  Its  volatile  character  is  the 
occasion  of  a  singular  appearance,  when  small  bits  of 
the  substance  are  thrown  upon  warm  water.  The  par- 
ticles are  seen  to  sail  about  as  if  they  were  possessed 
of  life,  owing  to  the  propelling  effect  of  the  vapor 
which  escapes  beneath  them.  ,/A— 

How  are  re-  961.    RESINS. — The   resins,   of   which 

sins  formed?  ordinary  pine  rosin  may  serve  as  an  exam- 
ple, are  formed  by  the  action  of  oxygen  upon  the  essen- 
tial oils.  Oil  of  turpentine  may  be  thus  partially  con- 
verted into  resin,  by  long  exposure  to  the  air.  On  sub- 
sequently heating  it,  only  a  portion  is  found  to  be  vola- 
tile, while  a  resinous  mass  remains  behind.  Turpen- 
tine, or  pitch  of  pine  trees,  is  thus  formed  in  nature, 
from  the  oil  of  turpentine,  as  it  exudes  from  the 
trees.  But  the  conversion  is  only  partial,  so  that  the 
turpentine  yields,  on  distillation,  a  portion  of  oil,  while 
rosin  remains  behind.  Resins  are  easily  distinguished 
from  gums  by  their  insolubility  in  water ;  they  are,  on 


384  ORGANIC    CHEMISTRY. 

the  other  hand,  readily  soluble  in  alcohol  or  ether. 
They  are  not  liable  to  decay,  like  most  other  substan- 
ces of  vegetable  origin.  Copal,  shellac,  mastic,  and 
amber,  are  all  resins.  The  latter  is  found  in  certain 
coal  mines,  and  at  the  bottom  of  the  sea,  and  has 
probably  had  its  origin  in  the  forests  of  some  primeval 
age. 

962.    EXPLANATION. — The    action    of 

Explain  the  ~     ,  ...  , 

above  trans-  the  oxygen  of  the  air,  m  the  above  case, 
formation?  ^  similar  to  that  which  occurs  in  the  con- 
version of  alcohol  into  vinegar.  A  portion  of  the  hy- 
drogen is  burned  out,  as  it  were,  and  removed  in  the 
form  of  water,  while  another  portion  of  oxygen  takes 
its  place. 

963.     USE   OF    THE    RESIN VARNISHES. 

what  use  is 

made  of  the  The  resins  are  principally  employed  for  the 
TarT varnishes  production  of  varnishes.  These  are  simply 
made?  solutions  of  resins  in  alcohol,  ether,  or 

spirits  of  turpentine  ;  or  an  intimate  mixture  of  the 
latter  with  fused  resin  and  oil.  In  preparing  copal  var- 
nish, which  is  the  most  brilliant  and  durable,  the  resin 
is  first  fused,  then  incorporated  with  heated  oil,  and 
afterward  diluted  with  spirits  of  turpentine.  A  com- 
mon varnish  for  maps,  engravings,  and  similar  objects, 
is  made  by  dissolving  mastic  with  a  little  Venice  tur- 
pentine and  camphor,  in  spirits  of  turpentine.  Pounded 
glass  is  added  to  the  pulverized  material  during  the 
process  of  solution.  The  object  is  covered  with  a  so- 
lution of  isinglass  before  using  this  varnish,  to  prevent 
its  absorption.  Shellac,  in  alcohol,  is  employed  to 
impart  to  wood  or  other  material  a  resinous  coating^ 


RESINS.  385 

which  is  afterward  polished  with  rotten  stone.  Copal 
varnish  is  also  similarly  used.  Shellac,  dissolved  in 
soda  or  potash,  is  sometimes  used  to  give  body  to 
paints,  as  a  substitute  for  part  of  the  more  expensive 
material. 

What  i«  rosin  964.  ROSIN  SOAP. — The  resins  possess 
soap?  an  acid  character,  and  like  fats,  form  soap 

with  the  alkalies.  Common  rosin  is  largely  consumed, 
with  fat  and  potash,  in  the  manufacture  of  common 
brown  soap.  The  greater  hardness  which  it  imparts 
depends  on  the  formation  of  a  certain  portion  of  rosin 
soap,  in  the  mixture. 

965.     SIZING. — The    soap     which    is 

How  is  rosin 

used  in  sizing  formed  on  boiling  rosin  with  strong  potash 
paper?  -g  uge(j  m  sjznig  paper.  Being  mixed  with 

the  material  from  which  paper  is  to  be  made,  a  solution 
of  alum  is  afterward  added  to  the  pulp,  and  a  compound 
of  rosin  and  alumina  thus  produced  in  every  portion  of 
the  mass.  The  pores  of  paper  made  from  this  mate- 
rial are  thus  completely  filled,  and  the  spreading  of 
the  ink  prevented.  A  surface  sizing  which  is  less  ef- 
fectual, is  also  given  to  paper  by  a  solution  of  glue, 
applied  after  the  paper  is  formed.  When  this  is  de- 
stroyed by  erasure,  its  place  may  be  supplied,  and  the 
spreading  of  ink  prevented,  by  rubbing  powdered  rosin 
upon  the  spot  from  which  the  sizing  has  been  removed. 
966.  SEALING-WAX. — Sealing-wax  con- 

What  is  the 

tionof   sists,  principally,  of  shellac.      Venice  tur- 
pentine is  added  to    make   it  more  inflam- 
mable and  fusible,   and  vermilion  or  lamp-black  to  color 

it.     Ship  pitch  is  resin   changed  and  partially  decom- 

17 


cotnposi 
sealing-icax  ? 


386  ORGANIC    CHEMISTRY. 

posed  by  heat.     Shoemakers  wax  is  made  by  a  similar 
process. 

What  are  the  ^67.      ROSIN     OIL     AND     GAS. Rosin     is 

products  of  partially  converted  by  dry  distilla- 
te dry  distil-  \         .  .  .  ,     . 

lation  of  tion  into  an  oil,  which  is  largely 


used  for  adulterating  other  oils,  and 
also  for  purposes  of  illumination.  A  black  pitch 
remains  in  the  retort.  The  oil  has  the  advan- 
tage of  extreme  cheapness,  but  owing  to  its 
large  proportion  of  carbon,  can  only  be  burned 
in  lamps  furnished  with  tall  chimneys.  At  a 
still  higher  temperature  rosin  is  converted  into 
gas,  with  a  residue  of  carbon. 

What  is  as-  968.    AspHALTUM. — Asphaltuni    or   bi- 

phaltum?  tumen  is  a  mineral  resin,  similar  to  the 
black  pitch  which  remains  from  the  distillation  of  coal 
tar.  This  material  is  found  on  the  shores  of  the  Dead 
Sea,  in  the  island  of  Trinidad,  and  in  several  European 
localities.  It  is  extensively  employed  for  hydraulic 
cements,  roofing,  and  pavements. 

969.  PETROLEUM. — Petroleum  is  a  liquid 

What  is  said  . 

of  the  source,  hydrocarbon,  also  known  as  rock  oil.  It  is 
often  found  uPon  standing  water,  in  bitu- 
ofpetrole-  minous  coal  districts.  Pits  are  also  dug 
for  the  purpose  of  collecting  it.  These 
become  filled  with  water,  upon  which  the  oil  rises,  more 
or  less  abundantly.  The  rectified  petroleum  is  called 
naptha,  and  is  a  nearly  colorless  and  highly  volatile 
fluid.  The  entire  absence  of  oxygen  in  its  composi- 
tion, adapts  it  perfectly  to  the  preservation  of  the  metals 
potassium,  and  sodium,  in  their  metallic  condition. 


CAOUTCHOUC.  387 

It  is  also  used  as  a  solvent  of  sulphur,  phosphorus,  fats, 
resins,  and  caoutchouc.  Both  asphaltum  and  petroleum 
have  been,  probably,  produced  by  the  action  of  vol- 
canic fires  upon  bituminous  coal. 

970.  GUM  RESINS. — The  dried  juices 

what  is  said  .  , 

of  gum  re-  of  certain  plants  consist  of  mixtures  of 
gum  and  resin.  These  mixtures  are  called 
gum  resins.  Water  dissolves  the  gum,  and  holds  the 
resin  in  suspension,  thus  forming  what  is  called  an 
emulsion.  Alcohol,  on  the  other  hand  extracts  the  re- 
sin from  their  mixtures.  Assafoetida,  gamboge,  and 
opium,  are  a  few  examples  of  gum  resins. 

971.  CAOUTCHOUC.     GUM     ELASTIC. — 

Mention  the  •        i       i  ' «  • 

sources  and  Caoutchouc  is  a  hydrocarbon,  obtained  from 
™outchouc°{  tne  milky  Juice  °f  certain  trees  in  Asia, 
Africa,  and  South  America.  This  constit- 
uent of  the  juice  hardens,  on  exposure  to  the  air,  while 
the  remainder  is  removed  by  evaporation.  By  the  ad- 
dition of  a  little  ammonia,  the  milk  may  be  retained  in 
its  liquid  condition.  Caoutchouc  is  soluble  in  ether, 
spirits  of  turpentine,  oil  of  coal  tar,  and  many  other 
hydrocarbons.  Sulphuret  of  carbon,  a  volatile  liquid 
obtained  by  passing  sulphur  vapors  over  ignited  char- 
coal, is  also  a  complete  solvent  of  India-rubber  and 
gutta  percha. 

972.  VULCANIZED  RUBBER. — Heated  for 

How  is  caout- 
chouc vulcani-    a  snort    time    with    sulphur,    at   280°,    or 

Zave  the^rl  -  somewnat  above  this  point,  caoutchouc 
ertiesof  mil-  becomes  remarkably  changed  in  its  nature, 

canized  "  rub-  -,    •  .  ~          ,    .  ,  ,  ,, 

ber?»  and  is  no  longer  stiffened  by  cold,  or  soft- 

ened by  heat.     It  is  then  called  vulcanized 


388  ORGANIC    CHEMISTRY. 

rubber,  and  constitutes  the  material  out  -  of  which 
most  India-rubber  goods  are  now  made.  The  hard 
rubber  which  is  extensively  employed  for  the  manu- 
facture of  cornbs,  knife-handles,  pencil-cases,  &c.,  is 
composed  of  pitch,  India-rubber,  sulphur,  and  mag- 
nesia. The  mixture  is  softened  at  about  270°,  then 
pressed  into  moulds  to  give  it  the  required  shape.  It 
is  afterward  wrought  like  ivory. 

Whatisgutta  973'  GUTTA  PERCHA.— Gutta  percha  is 
percha?  identical  in  composition  with  gum  elastic, 

Mention  some  ,       ,  _.„ 

of  its  proper-  but  possessed  of  quite  different  properties. 
ties  and  uses,  ^mong  them  is  its  extreme  toughness,  and 
comparatively  slight  elasticity.  It  is  rendered  soft  and 
plastic  by  immersion  in  boiling  water,  and  in  this  pasty 
condition  may  be  moulded  into  any  required  shape.  It 
can  be  vulcanized,  like  caoutchouc,  and  is  then  proof 
against  elevation  of  temperature.  It  is  employed  as  a 
substitute  for  caoutchouc  where  great  elasticity  is  not 
required.  Both  of  the  above  substances  approach  more 
nearly  in  their  composition  to  the  essential  oils,  than  to 
any  other  class  of  compounds. 

PROTEIN  BODIES— PUTREFACTION". 
Stated  com-  974'    VEGETABLE     FIBRIN.— The     glutin- 

position  and     ous  mass  which  remains  when  dough  is 

properties  of  .      . 

vegetable  kneaded  in  water    until  all  the  starch   is 

fibnn.  removed,    is  called   gluten     or   vegetable 

fibrin.  It  diners  from  all  the  organic  matter  hitherto 
described,  in  containing  nitrogen,  with  small  quantities 


VEGETABLE    ALBUMEN.  389 

of  sulphur,  and  phosphorus.  Its  exact  composition  is 
given  in  the  Appendix.  It  is  a  grey  substance,  and  is 
the  material  which  gives  its  cohesion  to  bread. 

975.  VEGETABLE  ALBUMEN  AND  CASEIN.  — 

What  is  said  .  •      -i  r. 

of  vegetable       Vegetable  albumen  is  a  similar  substance, 


contained,  ni  smaller  quantity,  in  the  juices 
of  fruits  and  vegetables.  It  is  coagulated 
by  heat,  like  the  white  of  egg,  when  the  juices  are 
boiled.  Vegetable  casein  is  another  substance  of  very 
similar  composition  and  properties,  found  principally 
in  the  seeds  of  leguminous  plants.  It  precipitates  like 
the  curd  in  sour  milk,  when  a  little  acid  is  added  to 
an  aqueous  extract  of  the  seeds.  These  substances 
derive  their  names  from  their  resemblance  to  animal 
fibrin,  albumen,  and  casein.  Vegetable  casein  is  also 
called  legumine.  All  of  these  substances  were  at  one 
time  supposed  to  be  compounds  of  a  single  substance, 
called  protein,  itself  free  from  both  sulphur  and  phos- 
phorus. Later  experimenters  have  not  succeeded  in 
isolating  such  a  substance,  and  the  theory  is  therefore 
abandoned.  The  name  is  retained  in  this  work  as  a 
convenient  designation  of  the  class  of  substances  here 
considered. 

976.    OCCURRENCE.  —  One    or  more   of 

Where  are  the 

above  subxtan-  these  substances  is  present  in  greater  or 
cesfuund?  legs  quantity  in  au  parts  of  piants.  They 

are  found  accumulated  with  starch,  in  the  fruit  and 
seed.  The  seeds  of  cereals,  such  as  wheat  and  rye, 
and  those  of  leguminous  plants,  such  as  peas  and  beans, 
contain  them  in  large  proportion. 


390  ORGANIC    CHEMISTRY. 

,r    ,  977.     CHARACTERISTICS.  —  If   a   bit   of 

Mention  a  pe- 

culiarity of       gluten  be  placed  on  the  end  of  a  wire  and 
burned,  a  very  different  odor  is  produced 


pounds.  from   that    of    burning    starch    or   wood. 

The  smell  approaches  that  of  burning  wool,  and  is  a 
means  of  distinguishing  organic  matter  which  contains 
nitrogen.  If  boiled  with  potassa,  the  sulphur  of  gluten 
is  extracted,  and  the  solution  will  blacken  paper  moist- 
ened with  sugar  of  lead.  This  reaction  furnishes  an- 
other means  of  detecting  nitrogenous  substances. 

978.  PUTREFACTION.  —  A  still  more  im- 

Describethe  .  *.'••.  i_ 

process  of  pu-  portant  distinction  of  nitrogenous  substan- 
trefaction.  ceg  from  those  which  contain  no  nitrogen, 
is  their  spontaneous  putrefaction.  Left  to  themselves, 
they  are  resolved,  like  blood  and  flesh  to  which  they 
are  allied  in  composition,  into  a  variety  of  other  pro- 
ducts. It  is  not  strictly  correct  to  say  that  this  decom- 
position is  spontaneous.  The  substance  must  first 
have  been  exposed  to  the  air.  An  oxidation  or  slow 
combustion  is  then  commenced,  which,  although  en- 
tirely imperceptible  in  its  effects,  and  checked  at  once 
by  exclusion  of  air,  ensures  the  subsequent  putrefac- 
tion. It  burns  out  a  small  portion  of  carbon  and  hy- 
drogen, and  thus  removes,  as  it  were,  the  key-stone  of 
the  arch  in  every  molecule.  The  atoms  may  then  be 
supposed  to  fall  together  and  re-arrange  themselves  as 
is  required  by  the  known  products  of  their  decompo- 
sition. 

979.  PRODUCTS  OF  PUTREFACTION.  —  The 

Mention  some  ^.  'L-%>  '  r 

products  of       re-arrangement  which  occurs  m   putrefac- 
ef  action.  consistSj  essentially,  in  the  combustion 


FERMENTATION.  391 

of  the  carbon  of  the  substance  with  oxygen,  while  the 
hydrogen  divides  itself  between  the  nitrogen,  phospho- 
rus, and  sulphur,  forming  ammonia,  phosphuretted  and 
sulphuretted  hydrogen.  It  is  to  these  gases  that  the 
offensive  smell  which  is  given  off  in  putrefaction  is 
principally  to  be  ascribed. 

980.  FERMENTATION. — Any  one  of  the 

What  substan-  .  , 

ce*  are  capable  nitrogenous  substances  above  mentioned, 
of  producing  hij  undergoing  the  change  which  is 

jermentation  ?  D 

called  putrefaction,  is  capable,  by  its  mere 
presence,  of  acting  as  a  ferment.  A  little  putrefying 
gluten,  for  example,  added  to  a  solution  of  sugar,  will 
convert  it  into  alcohol  and  carbonic  acid.  Here  again 
the  key-stone  of  the  molecule  is  removed,  or  rather  in 
this  case  moved.  The  motion  of  the  atoms  of  the 
putrefying  substance  would  seem  to  be  the  cause. 
The  effect  is  analogous  to  that  of  heat,  through  whose 
agency,  also,  complex  organic  bodies  are  resolved  into 
others  of  simpler  constitution. 

981.    YEAST. — The   first   stage   in    the 

What  is  the 

first  stage  in  formation  of  yeast  is  the  production  of  a 
the  process?  microscopic  vegetation,  which  consumes 
all  the  protein,  converting  it  in.to  the  substance  of  a 
microscopic  plant.  Ordinary  brewers'  yeast  is  such  a  mi- 
croscopic vegetation.  Being  produced,  it  passes  imme- 
diately into  the  putrefaction  above  described,  effecting, 
at  the  same  time,  the  conversion  of  any  sugar  which 
may  be  present  into  alcohol  and  carbonic  acid.  By 
some,  the  growth  of  the  microscopic  plant  itself,  instead 
of  its  subsequent  change,  is  supposed  to  be  the  cause 
of  fermentation. 


392  ORGANIC    CHEMISTRY. 


Holds  yeast  982.    PRODUCTION  OF  YEAST.  -  Yeast  has 

produced?  not  onjy  fae  pOwer  of  converting  sugar 
into  alcohol,  but  it  at  the  same  time  occasions  the 
production  of  more  yeast  from  dissolved  protein.  In 
the  ordinary  process  of  beer  brewing,  the  newly  formed 
yeast  collects  on  the  surface  of  the  fermenting  vats. 
It  is  thence  removed,  to  serve  as  the  excitant  of  a  new 
fermentation,  or  to  be  employed  in  the  production  of 
bread,  which  is,  chemically  considered,  an  analogous 
process. 

983.    DIFFERENT    KINDS    OF   FERMENTA- 

Mention  seve- 

ral kinds  of  TioN.  —  The  products  of  fermentation  are 
fermentation.  Different,  according  to  temperature  and 
other  circumstances.  Thus  the  same  sugar  which  at 
40°,  to  86°,  with  cheese  used  as  a  ferment,  yields  car- 
bonic acid  and  alcohol,  at  a  temperature  of  86°,  to  95° 
is  converted  into  lactic  acid.  The  latter,  by  the  further 
action  of  the  curd,  with  slight  elevation  of  tempera- 
ture, is  converted  into  butyric  and  carbonic  acids.  By 
the  same  ferment,  at  a  still  higher  temperature,  a  portion 
of  gum  is  produced  with  the  lactic  acid.  These  diffe- 
rent processes  of  transformation  have  received,  respec- 
tively, the  names  of  the  vinous,  lactic,  butyric,  and 
viscous  fermentations.  The  conversion  of  starch  into 
sugar  by  diastase  may  be  regarded  as  a  species  of  fer- 
mentation. This  substance  is  a  slightly  changed  glu- 
ten. It  is  always  produced  in  germination,  and  may 
be  precipitated  by  alcohol  in  the  form  of  white  flakes, 
from  a  concentrated  infusion  of  malt.  One  part  of  it 
is  sufficient  to  convert  two  thousand  parts  of  starch 
into  sugar. 


BREAD.  393 

What  is  said  984     FLOUR.— Fine  flour  makes  less 

of  the  nutri-      nutritious  bread  than  the  coarser  varieties. 

tious  proper-  .!*•*>* 

ties  of  fine  because  it  contains  a  smaller  proportion  of 
gluten.  Gluten  being  tougher  than  the 
starch,  is  not  reduced  to  so  fine  a  powder,  and  is  par- 
tially separated  in  the  process  of  bolting.  All  grains 
contain  sugar  in  small  proportion.  Sugar  is  therefore 
one  of  the  constituents  of  flour. 

Whatchemi-         ^85.  BREAD. — The  " raising"   of  bread 
cat  principles   is  a  process  of   fermentation.     The  yeast 

are  involved 

in  making  employed  in  the  process  converts  a  portion 
of  the  starch  of  the  flour  into  sugar,  and 
subsequently  into  alcohol  and  carbonic  acid.  The 
sponge  is  made  light  and  porous,  by  the  gas  bubbles 
which  become  entangled  within  it.  A  large  part  of 
the  alcohol  produced  in  the  process  escapes  into  the 
oven,  and  thence  into  the  exterior  air.  It  may  be 
condensed  and  converted  into  spirits  by  the  proper 
apparatus.  This  has  been  successfully  done  in  large 
bakeries  in  Europe,  but  the  process  has  not  been  found 
to  be  of  any  considerable  economical  importance.  In 
the  process  of  baking  a  portion  of  starch  is  converted 
into  gum.  By  moistening  the  baked  loaf  with  water 
the  gum  is  dissolved,  and  by  a  new  heating,  hardens 
into  the  shining  surface  which  is  often  observed  on 
bakers'  bread. 

What  materi-        986-  YEAST  POWDERS.— The  gas  which 
ais  are  some-     is  needed  to  make   bread  lia:ht,  may  be 

times  substi- 
tuted for  produced  by  other  means  than  the  process 

yeast  /  of  fermentation.     If  carbonate  of  soda,  for 

example,  is  kneaded  into  the  dough,  and  tartaric  acid 
17* 


394  ORGANIC    CHEMISTRY. 

subsequently  added  in  proper  proportion,  the  weaker 
carbonic  acid  is  expelled.  A  light  sponge  is  produced 
by  its  escape,  without  the  loss  of  the  starch  and  sugar 
which  are  consumed  in  the  process  of  fermentation. 
Soda  and  tartaric  acid  prepared  for  this  purpose  are 
known  under  the  name  of  yeast  powders.  Carbonate 
of  ammonia  being  entirely  volatile  by  heat,  may  be 
employed  alone  for  the  same  purpose.  A  portion  of 
the  salt  probably  remains  in  the  bread,  and  is  more  or 
less  injurious,  on  account  of  its  alkaline  character. 

987.   TEST  FOR  YEAST  POWDERS. — The 

What  is  the  .  .  f     , 

objection  to        great  objection  to  the  use   of  these  pow- 

*faUinlfreadf  ^GYS  *u  the  PreParation  °f  bread,  consists 
in  their  liability  to  contain  soda  or  acid  in 
undue  proportion.  Whether  this  is  the  case,  may  be 
ascertained  by  dissolving  the  powders  in  water,  and 
mixing  the  solutions.  If  the  product  is  neutral  to  the 
taste  and  does  not  effervesce  on  the  addition  of 
either  soda  or  acid,  this  fact  will  be  evidence  of  their 
proper  preparation.  If  otherwise,  more  or  less  injury 
is  to  be  anticipated  from  their  use.  Excess  of  the  al- 
kalies especially  interferes  with  the  process  of  diges- 
tion, by  neutralizing  the  acids  which  accomplish  it. 
The  use  of  soda  and  saleratus  with  sour  milk  is  liable 
to  the  same  objections. 

What  is  said,  ^88.       THEIR    EFFECT     ON     HEALTH. It 

Ihe^rfffe^'on  ma^  wel1  be  <lliestioned  whether  bread 
the  health  ?  prepared  by  this  process,  is  ever  as  healthy 
as  that  made  with  yeast.  For  even  the  neutral  tar- 
trate,  formed  when  the  materials  are  used  in  proper  pro- 
portion, will  tend  to  neutralize  certain  stronger  acids, 


ALKALOIDS.  395 

which  are  constituents  of  the  gastric  juice.  It  may 
thus  interfere,  in  a  measure,  with  the  process  of  diges- 
tion. If  pure  muriatic  acid  were  substituted  for  the 
tartaric  acid  or  cream  of  tartar,  this  objection  would  be 
removed.  The  product  of  its  action  on  soda  is  com- 
mon salt. 

ORGANIC  BASES. 

989.  ALKALOIDS. — Morphine  and  strych- 
namesofsome  nine,  the  former  a  useful  medicine,  and 
fold™  alWh  the  latter>  tlie  most  dreadful  of  poisons,  are 
are  they  so  examples  of  the  alkaloids.  They  are 
white  crystalline  bodies,  but  slightly  solu- 
ble in  water.  Most  of  them,  like  the  protein  bodies 
above  mentioned,  contain  the  four  organic  elements  ; 
but  they  differ  widely  from  these  substances,  in  possess- 
ing a  positive  chemical  character.  They  are  called 
alkaloids  from  their  resemblance,  in  certain  properties, 
to  the  alkalies  of  inorganic  chemistry.  Their  action 
upon  vegetable  colors  is  the  same  ;  like  the  alkalies, 
they  also  form  salts  with  both  organic  and  inorganic 
acids.  They  are,  in  fact,  true  alkalies.  Their  alkaline 
property  does  not,  however,  seem  to  depend  on  the 
oxygen  which  they  contain.  Some  of  them,  indeed, 
do  riot  contain  this  element.  It  is  highly  probable  that 
certain  of  the  alkaloids  belong  to  the  class  of  compound 
ammonias  mentioned  in  the  first  chapter  of  Organic 
Chemistry. 

What  is  their  990.  Their  action  on  the  human  body 
action  on  the  does  not  depend  upon  their  alkaline  char- 

human  body  ? 

Thdr  anti-  acter,  but  on  other  and  peculiar  properties 
***'  belonging  to  each.  The  salts  of  the  alka- 


396  ORGANIC    CHEMISTRY. 

loids  are  generally  preferred  in  medicine,  in  view  of 
their  ready  solubility.  In  large  doses  they  are  all 
poisonous.  The  tincture  of  nut-galls  is  employed  as 
an  antidote,  because  of  the  property  of  the  tannic  acid 
which  it  contains,  to  form  with  most  of  the  alkaloids 
insoluble  precipitates. 

991.  OCCURRENCE. — Morphine  is   con- 

Wfiat  is  the  .  r 

source  of  the  tamed  in  opium,  qmmne  is  extracted  from 
alkaloids  ?  Peruvian  bark,  and  strychnine,  from  the  nux 
vomica.  The  latter  is  also  the  poison  of  the  celebrated 
upas.  Theine  and  nicotine  are  other  alkaloids,  the 
former  of  which  is  found  in  tea  and  coffee,  and  the  latter 
in  tobacco.  Theine  may  be  obtained,  as  a  sublimate 
of  silky  crystals,  by  moderately  heating  tea  in  an  iron 
pot  covered  with  a  paper  cone. 

992.  PREPARATION. — Most  of  the  alka- 

How  are  the 

alkaloids  ex-  loids  may  be  extracted  from  the  material 
which  contains  them  by  means  of  acidu- 
lated water.  A  salt  of  the  alkaloid  is  thus  obtained  in 
solution.  From  this  salt  the  alkaloid  may  be  precipi- 
tated, like  oxide  of  iron  or  any  other  base,  by. am- 
monia. Nicotine  is  a  most  energetic  poison,  falling 
scarcely  below  prussic  acid  in  its  destructive  properties. 

COLORING  MATTERS. 

What  is  said  993.  INDIGO. — The  vegetable  dye-stuffs 
of  indigo?  are  extremely  numerous.  Indigo,  madder, 
and  logwood  are  among  the  more  important.  Indigo 
is  deposited  from  the  colorless  juice  of  certain  plants 
by  simple  exposure  to  the  air.  It  may  be  sublimed  in 


DYEING.  397 

purple  crystals,  by  rapid  heating.  By  removing  the 
oxygen  absorbed  in  its  production,  the  original  color- 
less juice  may  be,  as  it  were,  reproduced  from  commer- 
cial indigo.  This  object  is  effected  by  the  use  of  pro- 
tosulphate  of  iron,  which  is  converted  into  sulphate  of 
the  peroxide  in  the  process.  Caustic  lime  is  at  the 
same  time  added  to  dissolve  the  deoxidized  indigo. 
The  colorless  solution  is  employed  in  dyeing  ;  cloth  im- 
pregnated with  it  becomes  blue  on  exposure  to  the 
air.  A  solution  of  indigo  in  concentrated  sulphuric 
acid  is  also  employed  in  dyeing. 

Wh,at  is  mad-  994.  MADDER. — Madder  is  the  ground 
der?  root  Of  t^  rulia  tinctoriutn.  This  plant 

is  cultivated  extensively  in  India  and  Europe.  It  con- 
tains a  red  dye,  produced  by  the  action  of  the  'air  or 
certain  chemical  agents,  upon  the  juices  of  the  recent 
plant.  This  body  is  called  alizarine,  and  may  be  ob- 
tained in  beautiful  crystals.  An  infusion  of  the  root  in 
hot  water  contains  a  portion  of  this  substance  in  solution. 
What  is  log-  995.  LOGWOOD. — This  is  a  red  wood, 
wood?  obtained  from  Spanish  America  and  much 

employed  in  dyeing.  Its  coloring  matter  is  called  he- 
matoxyline.  By  evaporating  a  decoction  of  the  wood 
and  re-dissolving  in  alcohol,  this  substance  may  be  ob- 
tained, on  a  second  evaporation,  in  the  form  of  yellow 
crystals. 


DYEING. 
996.    DYEING. — Few  dves  can  be  per- 

Explain  the  * 

theory  of  dye-     manently  imparted  to  cloth  without  the  in- 

ing  fast  colors.     tervention  Qf  some  third  substance,  which 


398  ORGANIC    CHEMISTRY. 

shall,  as  it  were,  hold  them  together.  Such  a  substance, 
with  strong  affinity  for  the  coloring  matter  of  the  dye, 
and  also  for  the  fibre  of  the  cloth,  is  called  a  mor- 
dant. The  fabric  to  be  dyed  being  first  impregnated 
with  the  mordant,  is  then  introduced  into  the  dyer's 
vat  to  receive  its  permanent  color. 
What  is  said  997.  MORDANTS.—  Alumina  and  oxide  of 
of  mordants?  jron  are  fae  principai  mordants  employed. 

They  may  be  "  fixed  "  in  the  cloth  by  immersion  in  the 
acetates  of  these  oxides.  A  subsequent  exposure  for 
several  days  to  the  air  is  essential,  in  order  that  the 
acetic  acid  may  in  part  be  expelled.  A  portion  of  it, 
however,  remains,  so  that  the  oxides  are,  strictly  speak- 
ing, in  the  condition  of  basic  acetates.  After  this  ex- 
posure, and  subsequent  washing  in  hot  water,  the  fabric 
may  be  immersed  in  the  dye.  An  ounce  of  madder 
heated  with  a  pint  of  water  will  be  sufficient  for  an 
experiment.  The  fabric  is  to  be  boiled  for  an  hour  or 
more  with  the  unstrained  decoction. 

998.   PREPARATION  OF  THE  MORDANT.  — 

How  is  the  alu-  . 

minous  mor-      The  solution    of   acetate    of    alumina   is 


most  conveniently  prepared  from  alum,  by 
the  substitution  of  acetic  for  its  sulphuric 
acid.  This  is  accomplished  by  the  addition  of  acetate 
of  lead.  Sulphate  of  lead  is  at  the  same  time  precipi- 
tated, and  may  be  filtered  off  from  the  acetate  which  is 
formed.  Three  pounds  of  alum  and  two  of  sugar  of 
lead,  to  three  gallons  of  water,  are  the  proportions  to 
be  employed.  This  mordant  produces  a  red  color. 

How  are  vari-  999.     VARIOUS     COLORS     BY     THE      SAME 

ous  colors  pro-    DYE  —  gy   faQ  use  of  different   mordants. 

ducedfrom  one 

dye?  various  colors  may  be  produced  from  the 


MINERAL    DYES.  399 

same  dye.  Substitute  four  pounds  of  green  vitriol  for 
the  alum  used  in.  the  previous  case,  and  the  madder 
gives  a  deep  black.  Add  four  ounces  of  arsenic  with 
the  green  vitriol,  and  a  mordant  is  produced  with  which 
the  dye  will  yield  a  beautiful  purple.  In  the  latter 
case,  the  solution  must  be  reduced  to  one-tenth  of  its 
original  strength  by  the  addition  of  water. 

1000.  DYEING  WITH  LOGWOOD. — By  the 
briefly  the  pro-  employment  of  the  last  two  mordants, 
with  °lo  dwood9?  mixed  m  equal  proportions  and  diluted  with 
an  equal  quantity  of  water,  a  mordant  for 
dyeing  black  with  logwood  is  obtained.  For  dyeing 
purple  with  the  same  material,  a  tin  mordant  is  used. 
It  may  be  prepared  by  dissolving  tin  in  muriatic  acid, 
with  the  gradual  addition  of  nitric  acid,  then  precipi- 
tating and  re-dissolving  with  potassa.  The  cloth  being 
impregnated  with  this  mordant  and  thoroughly  dried, 
is  passed  through  dilute  sulphuric  acid,  to  remove  the 
potassa  and  leave  the  oxide  of  tin.  After  subsequent 
drying  and  exposure  to  the  air,  the  fabric  is  ready  for 
the  dye. 

What  are  1001.    MINERAL    DYES. The     dyes    de- 

minerai  dyes?  scriDed  in  the  following  paragraphs,  are 
distinguished  from  those  before  mentioned,  by  contain- 
ing no  organic  matter.  They  consist  of  colored  salts  or 
oxides,  precipitated  in  the  fibre  of  the  cloth.  Although 
these  substances  belong,  strictly  speaking,  to  inorganic 
chemistry,  they  are  here  introduced  to  complete  the 
survey  of  the  subject  of  dyeing  and  calico  printing. 

1002.  PRUSSIAN  BLUE. — A  mineral  blue 

How  is  a  min- 
eral blue  ob-      may  be  produced  by  impregnating  cloth 
tamed?  ^^  ^  soiution  of  acetate  of  iron,  before 


400  ORGANIC    CHEMISTRY. 

described  as  a  mordant,  and  then  immersing  it  in  an 
acidified  solution  of  prussiate  of  potash.  Prussian  blue 
is  thus  precipitated  in  the  cloth.  This  blue  is  found  to 
be  brightened  by  passing  it  through  a  solution  of  sugar 
of  lead. 

1003.  MINERAL  GREEN. — A  mineral  green 

How  is  a  min-     .*-.., 

eraigreenpro-  is  produced  in  the  same  manner  by  the  em- 
duced?  ployment  of  sesquichloride  of  chromium, 

and  subsequent  immersion  in  potassa.  The  color  con- 
sists of  sesquioxide  of  chromium,  precipitated  from  the 
chromium  salt  by  the  action  of  the  alkali.  The  so- 
lution of  sesquioxide  of  chromium  is  prepared  by  the 
addition  of  sugar  to  a  solution  of  bichromate  of  potassa 
in  dilute  sulphuric  acid.  A  part  of  the  oxygen  of  the 
chromic  acid  being  abstracted  by  the  organic  matter,  it 
is  converted  into  an  oxide,  which  remains  in  solution. 

1004.  CHROME  YELLOW. — To  produce  a 

How  is  a  min-         .  . 

eral  yellow  mineral  yellow,  the  cloth  may  be  impreg- 
produced?  nated  with  acetate  or  nitrate  of  lead,  then 
dried  and  passed  through  sulphate  of  soda,  to  fix  the 
lead  as  sulphate  in  the  cloth.  On  finally  immersing 
it  in  bichromate  of  potassa,  the  cloth  becomes  dyed 
with  yellow  chromate  of  lead.  The  above  process 
modified  by  printing  instead  of  saturating  with  acetate 
of  lead,  gives  yellow  figures  on  a  white  ground. 

CALICO  PRINTING. 

How  is  a  white  1005.  WHITE  FIGURES. — If  it  is  desired 
^oods  °rodyed  t0  obtain  a  design  in  white,  on  goods  dyed 
duced?  with  either  of  the  above  madder  colors, 


CALICO    PRINTING.  401 


HXY 


the  design  is  printed  with  a 
paste  of  tartaric  acid  upon  the 
colored  cloth.  On  subsequently 
immersing  the  goods  in  a  bath 
of  chloride  of  lime,  chlorine  is  evolved  in  the  tissue, 
and  the  color  discharged  only  where  the  acid  is  printed. 
The  white  thus  produced  is  of  course  in  exact  cor- 
respondence with  the  printed  design. 

Howareyellow  1006-    PANTED  YELLOW  AND  BLUE.— To 

and  blue  de-       produce  yellows  on  madder  red  and  purple 

signs  obtained    ' 

on  dyed  grounds,  before   described,  tartaric  acid  is 

grounds  t  printed  with  the  nitrate  of  lead,  and  the 
cloth  immersed  in  bleaching  liquid.  The  color  of  the 
printed  portions  is  discharged  by  the  combined  action 
of  the  acid  and  bleaching  liquor ;  the  lead  is  at  the 
same  time  fixed  in  the  cloth,  as  chloride  of  lead.  On 
subsequent  immersion  in  bichromate  of  potassa,  the 
yellow  figures  of  ehromate  of  lead  are  produced  as  be- 
fore. For  blues  on  the  same  colored  grounds,  a  mix- 
ture of  Prussian  blue,  dissolved  in  bichloride  of  tin, 
with  tartaric  acid,  is  printed  on  the  cloth.  The  dis- 
charge of  the  ground  color  beneath  the  figure,  is 
effected,  as  before,  by  chloride  of  lime. 

1007.   VARIEGATED    PATTERNS. — All    of 

How  are  varie-  •.•«_• 

gated  patterns  the  madder  colors  which  have  been  men- 
produccd  ?  tioned,  may  be  produced  upon  a  single  piece 
of  white  goods,  by  printing  the  different  figures  of  the 
pattern  with  different  mordants.  This  is  accomplished 
by  passing  the  fabric  between  different  sets  of  rollers, 
each  of  which  is  supplied  with  a  paste  of  the  proper 
mordant,  and  so  engraved  that  it  yields  the  desired  im- 


402  ORGANIC    CHEMISTRY. 

pression.  On  subsequently  introducing  the  goods  into 
the  madder  bath,  the  various  colors  are  developed.  The 
whole  piece  is  at  the  same  time  transiently  colored  ; 
but  the  dye  may  be  readily  removed  from  the  imprinted 
portion  by  thorough  washing.  A  white  ground  for  the 
colors  is  thus  obtained. 

RELATION  OF  PLANTS  TO  THE  SOIL. 

AGRICULTURAL    CHEMISTRY. 

1008.    The  mineral  substances  which 

What  mineral       ,  ,  _,    .       ,.  .  .,  ,  , 

substances  do  plants  obtain  from  the  soil,  are  known  by 
plants  obtain  anaiysis  of  the  ashes  which  they  yield  on 

from  the  soil  ?  J    J 

combustion.  They  consist  of  acids  and 
bases,  which  enter  into  the  composition  of  all  fertile 
soils.  The  bases  are  potassa,  lime,  magnesia,  and 
oxides  of  manganese  and  iron.  These  are  found  com- 
bined in  the  ashes  with  silicic,  sulphuric  and  phosphoric 
acids,  and  are  accompanied  by  small  proportions  of 
common  salt.  The  carbonic  acid  which  is  found  in 
certain  ashes  is  produced  in  the  combustion  of  the 
plant.  The  ashes  of  all  cultivated  plants  contain  the 
above  substances  ;  but  in  different  proportions  accord- 
ing to  the  nature  of  the  plant.  The  phosphates  pre- 
dominate in  grains  ;  lime  exists  in  large  proportion  in 
grasses  ;  potash  in  edible  roots ;  and  silica  in  straw.  The 
approximate  composition  of  the  ash  of  different  plants 
is  given  in  a  table  in  the  Appendix.  In  estimating  the 
relative  proportions  of  the  different  constituents  which 
are  abstracted  from  the  soil  by  different  crops,  the  quan- 
tity of  the  crop,  as  well  as  the  composition  of  its  ash, 
is  of  course  to  be  brought  into  this  account. 


CONSTITUENTS  OF  SOILS.  403 

1009.  COMPOSITION  OF  SOILS.  —  Many  of 

Of  what  are  J 

soils  com-  the  above  substances  are  contained  in  the 
pose  '  soil  in  extremely  small  proportion.  Soils 

are  principally  composed  of  vegetable  matter  in  a  state 
of  decay,  with  clay,  sand,  and  carbonate  of  lime.  The 
vegetable  matter  consists  of  the  remains  of  plants  of 
previous  years,  and  the  clay,  lime,  and  sand,  are  the 
product  of  the  gradual  crumbling  and  decomposition 
of  rocky  crust  of  the  earth. 

1010.  USE   OF  VEGETABLE   MATTER  IN 

State  the  uses 

of  vegetable  SOILS.  —  The  wood,  leaves,  and  twigs  of 
™oihT  m  which  vegetable  matter  is  composed,  fur- 
nish, in  their  gradual  decay,  the  potash, 
silica,  and  other  constituents  of  their  own  skeletons  to 
form  the  framework  of  new  plants.  The  organic  mat- 
ter is,  at  the  same  time,  converted  into  ammonia  and 
carbonic  acid  ;  these  constitute  the  gaseous  food  on 
which  all  vegetable  life  is  sustained. 

1011.  ADDITION  OF  VEGETABLE  AND  ANI- 
K$Zd    -AL  MATTER._The  addition  of  more   of 
by  the  addi-       this  material  to  the  soil,  in  the  form  of  peat 

tion  of  vegeta-  -  •         /• 

bh  and  animal    or  muck  from  swamps,  is  of  great  advan- 


taSe?  because  it  increases  the  supply  of  the 
two  important  classes  of  materials  which 
have  been  mentioned.  Animal  matter  of  all  kinds, 
whether  decomposed,  as  in  stable  manure  and  guano, 
or  in  its  original  condition  in  the  form  of  flesh,  wool, 
and  bones,  is  a  still  more  valuable  addition  to  the  soil. 
The  reason  of  its  higher  value,  consists  in  the  fact 
that  while  it  yields  most  of  the  other  substances  which 
decaying  vegetable  matter  supplies,  it  furnishes  ammo- 


404  ORGANIC    CHEMISTRY. 

nia,  which  is  the  rarest  and  most  expensive  one,  in 
much  larger  proportion. 

1012.  USE  OF  THE  CLAY.  —  The  clay  in 

What  purpose  . 

does  day  sub-     soils   serves  to   retain  the    ammonia   and 


e  certam  otner  valuable  materials,  which 
would,  otherwise,  be  washed  away  by 
descending  rains.  It  seizes  not  only  upon  that  which 
comes  from  the  decaying  humus,  but  finds  particles  in 
the  drops  of  every  shower,  which  it  stores  safely  away 
for  the  future  use  of  the  plant.  It  serves  also  to  retain 
moisture  in  the  soil,  and  to  impart  to  it  the  tenacity 
by  which  the  roots  are  enabled  to  gain  a  firm  hold  upon 
the  earth.  Soils  which  contain  but  a  small  proportion 
of  clay  are  for  these  reasons  improved  by  its  addition. 

1013.  USES  OF  THE  SAND.  —  Sand,  where 

What  is  the 

office  of  sand  it  exists  in  due  proportion,  gives  the  proper 
tn  wist  degree  of  porosity  to  the  soil,  and  thus 
ensures  the  entrance  of  the  air  and  fertilizing  liquids, 
and  the  draining  away  of  all  excess  of  water.  Access 
of  air  is  important,  because  it  brings  with  it  fertilizing 
ammonia  and  carbonic  acid,  and  by  accelerating  the 
decay  of  vegetable  matter,  produces  more  of  these 
valuable  substances. 

1014.  USES  OF  THE  LIME.  —  The  lime  in 

What  is  the  -,  .          ,  ,      -,  -,  • 

office  of  lime  soils,  beside  serving  directly  as  building 
on  the  soil?  material  for  all  forms  of  vegetation,  is  the 
key  which  unlocks  other  treasures  of  the  soil  and  sup- 
plies them,  also,  to  the  growing  plant.  The  building 
material  which  is  furnished,  as  before  explained,  by 
the  decay  of  previous  plants,  is  not  sufficient.  A  por- 
tion of  it  never  reaches  the  fields  from  which  it  was 


ACTION  OF  LIME.  405 

originally  derived.  Exported  in  the  form  of  grain,  or 
milk,  or  beef,  it  returns  to  the  soil  in  some  distant  re- 
gion or  is  poured  into  the  rivers  and  the  sea  through 
the  drains  of  populous  cities.  New  supplies  of  potash 
and  other  material,  are,  therefore,  demanded  by  the 
vegetation  of  every  successive  year. 

1015.  A  large  part  of  the  materials  re- 

How  docs  it  . 

accomplish  the  ferred  to  are  locked  up  in  hard  grains  of 
object  ?  granite,  or  other  silicates  which  are  found 

in  the  soils.  Being  insoluble  in  water  and  the  other 
solvents  of  the  soil,  they  are  inaccessible  to  the  plant. 
Lime  has  the  property  of  forcing  itself  into  the  rocky 
prison  of  every  such  insoluble  grain,  and  setting  part 
of  its  inmates  at  liberty.  At  the  same  time  it  opens 
the  door  to  the  action  of  other  agencies  which  liberate 
the  rest.  They  are  then  floated  away  in  the  water 
which  penetrates  the  soil,  and  being  in  due  season  ab- 
sorbed, are  built  into  the  substance  of  the  plant. 

1016.  ACTION  OF  LIME  ON  MINERAL  MATTER 

Give  the  chem-  ......,,  ,         ...  . 

ical  explana-        EXPLAINED. The    actlOll    of    lime,    Which 

tfon  US  a°~  nas  Just  been  mentioned,  is  a  simple  conse- 
quence of  its  basic  properties.  It  takes 
possession  of  part  of  the  silicic  acid  of  the  alkaline 
silicate  in  the  rocky  grains.  Their  potassa  and  soda 
being  now  combined  with  this  acid  in  small  proportion, 
are  soluble  in  the  water  which  penetrates  the  soil. 

10 17.   The  water  of  the  soil  always  con- 

What  other  .  .  •/--.••  j 

decomposing      tains  a  certain  proportion  01  carbonic  acid. 
as%™st/xist'sin  This  acid  being  itself  material  for  vege- 
table  nutrition,   has  also  the  property  of 
dissolving  those  mineral  substances   which  the  plant 


--P  • 

406  ORGANIC    CHEMISTRY. 

needs  for  its  support.  By  the  joint  action  of  carbonic 
acid  and  water,  this  transfer  is  constantly  going  on 
even  without  the  aid  of  lime.  But  the  latter  substance 
very  much  accelerates  the  action,  arid  thus  adds  greatly 
to  the  fertility  of  the  soil. 

1018.  ACTION  OF  LIME  ON  ORGANIC  MAT- 

Mention  an-  .  . 

other  use  of  TER.  —  Lime  has  another  important  enect 
lsoil°nihe  on  so^s'  m  hastening  the  decomposition 
of  their  organic  matter,  and  thus,  indi- 
rectly, supplying  in  large  quantity,  valuable  materials, 
before  mentioned,  which  these  are  adapted  to  furnish. 
As  this  decomposition  proceeds  in  the  presence  of  lime, 
part  of  the  nitrogen  of  the  organic  matter  takes  the  form 
of  ammonia,  and  part  is  converted  into  nitrates,  as  will 
be  remembered  from  the  chapter  on  Salts.  But  the 
proportion  of  either  is  practically  immaterial,  as  both 
are  found  to  subserve  a  similar  purpose  in  building  up 
the  plant. 

1019.  All   of  the   effects    which    have 
*      been  mentioned,  may  be  regarded  as  grad- 


tioned  effects      ually  produced  in  every  soil  which  contains 

increased  ? 

Mention  an-      carbonate  of  lime  as  a  constituent.     When 


°  it;  is  deficient  in  quantity,  they  are,  of 
course,  increased  by  its  addition  in  the 
form  of  chalk  or  marl,  or  limestone.  These  substances 
have  also  the  effect  of  sweetening  peaty  and  marshy 
soils,  which  are  rendered  sour  from  the  presence  of  too 
large  a  proportion  of  vegetable  matter,  and  thus  ren- 
dering them  fit  for  cultivation. 

1020.   BURNED  LIME.  —  Burned  or  caustic 

In  what  form 

has  lime  the  lime  has  all  these  effects  in  a  much  greater 
degree,  and  therefore  its  extensive  use  as 
a  fertilizer  of  the  soil.  It  should  be  used 


GUANO.  407 

cautiously  on  soils  which  contain  but  a  small  propor- 
tion of  vegetable  matter,  for  fear  that  in  the  more  rapid 
decomposition  which  it  stimulates,  it  may  entirely 
exhaust  the  soil  of  this  material.  If  employed  in  such 
cases  it  should  be  with  admixture  of  vegetable  matter, 
that  the  loss  which  it  occasions  may  be  completely 
replaced. 

1021.   EFFECT    OF    ASHES    ON    SOILS. — 

What  other         _  .   . 

substances  act  Potassa  or  soda  applied  in  the  caustic  state, 
similarly?  Qr  ag  carbonates  have  entirely  analogous 

What  caution 

is  to  be  observ-    effects  on  the  soil.     They  render  the  in- 

edin  their  use?  ,    ,  ,  .' 

soluble  silicates  soluble,  by  increasing  in 
them  the  proportion  of  base,  and  also  hasten  the  decay 
and  conversion  of  vegetable  matter.  The  admixture 
of  lime  or  ashes  with  guano  or  decomposed  manure,  is 
to  be  avoided,  because  of  their  effect  to  expel  the 
ammonia  which  these  substances  contain.  This  may 
be  avoided  by  previously  incorporating  the  material 
with  a  large  proportion  of  clay  or  vegetable  mould, 
which  shall  serve  as  an  absorbent  of  the  liberated 
gas. 

What  is  said  1022.    COMPOSTS. CompOStS    COllsist  of 

of  composts?  vegetable  and  other  matter,  heaped  to- 
gether for  fermentation  and  partial  decay,  in  order  to 
prepare  them  for  application  to  the  soil.  In  such  mix- 
tures, all  alkaline  materials,  including  lime,  have  an 
effect  similar  to  that  which  they  produce  upon  the 
organic  matter  of  the  soil. 

Whatisgua-  1023.  GUANO. — Guano  consists  of  the 
no?  accumulated  droppings  of  birds,  and  is 

principally  obtained  from  certain  rocky  islands  on  the 


408  ORGANIC    CHEMISTRY. 

coast  of  South  America.  In  these  haunts  of  the  heron 
flamandj  and  other  sea-fowl,  it  is  accumulated,  in  some 
instances,  to  the  depth  of  a  hundred  feet.  The  de- 
posit is  usually  in  smaller  quantity,  but  amounts  in  the 
aggregate  to  millions  of  tons.  The  material  was  em- 
ployed as  a  fertilizer  by  the  natives  of  Peru  and  Chili, 
long  before  its  introduction  into  England  or  the  United 
States  for  the  same  purpose. 

1024.   DIFFERENT  VARiETiES.-The  qual- 

Whatiisaid  ...  ... 

of  different       ity  of  guano  differs  materially,   according 
to  tlie   source  fr°m  which    it  is  derived. 


The  ammoniacal  salts,  on  which  its  agency 
as  a  fertilizer  principally  depends,  being  soluble  in 
water,  the  product  of  moist  climates  is  of  comparatively 
little  value.  The  best  is  obtained  from  the  coast  of 
Peru,  where  rain  seldom  or  never  falls.  The  African, 
Patagonian  and  other  varieties,  are  much  inferior. 

In  what  does  1025'    AGRICULTURAL     VALUE.—  The  ag- 

theagricui-       ricultural  value  of  guano    lies  principally 

tural  value  .  . 

of  guana  m  the  ammonia  and  phosphate  of  lime 
depend?  which  it  is  capable  of  yielding  to  plants. 

These  constitute,  in  the  best  varieties,  about  one-third 
of  the  whole  weight.  Part  of  the  ammonia  is  ready 
formed,  and  part  is  produced  in  the  subsequent  change 
which  the  nitrogenous  matter  of  the  guano  experiences 
in  the  soil.  The  latter  may  be  produced  immediately 
by  a  chemical  process,  and  its  quantity  accurately 
determined.  In  estimating  the  value  of  guano,  it  is 
customary  to  record  the  quantity  of  this  potential  am- 
monia,  as  if  it  were  an  existing  constituent. 


SOILS.  409 

What  is  said  1026.    ARTIFICIAL    AMMONIA. The    COI1- 

of  the  artifi-     stituents  of  the  ammonia  which  we  pur- 

cial  produc-  ..  ~ 

tionofammo-  chase,  in  the  form  of  guano,  at  so  great 
expense  and  bring  from  distant  regions  of 
the  earth,  exist  in  unbounded  quantity  at  our  very 
doors.  Four-fifths  of  the  atmosphere  are  nitrogen  gas, 
and  the  ocean  is  an  exhaustless  reservoir  of  hydrogen. 
But,  strange  to  say,  the  chemist  with  all  his  skill, 
cannot,  except  by  circuitous  and  expensive  methods, 
effect  their  combination.  The  discovery  of  some  cheap 
and  ready  means  of  accomplishing  this  object,  would 
transform  the  face  of  the  earth,  by  the  unlimited  quan- 
tity of  fertilizing  material  which  it  would  supply.  This 
result  may,  perhaps,  be  reached  by  patient  investiga- 
tion. But  no  sudden  triumph  over  nature  need  be 
anticipated.  Improvements  in  Agriculture  will,  as  a 
general  thing,  be  only  realized  by  the  earnest  co-opera- 
tion of  scientific  and  practical  men,  in  laborious  and 
oft-repeated  experiment. 

1027.     EXHAUSTION    OF    SOILS. — When 

What  is  said  i     *   «  , 

of  the  exhaus-  soils  become  exhausted  01  those  substances 
tion  of  soils?  which  form  the  mineral  food  of  plants,  the 
growth  of  vegetation  ceases.  It  is  never  absolute, 
but  consists  in  a  great  reduction  of  that  portion  of 
their  material  which  is  in  a  condition  to  be  appropri- 
ated by  the  growing  plant.  Such  soils  are  gradually 
restored  by  rest.  A  gradual  decomposition  of  their 
insoluble  material  occurs  by  means  of  agencies  which 
have  before  been  mentioned,  and  the  soil  is  thus  re- 
stored to  its  original  condition.  These  effects  are  very 
much  hastened  by  plowing  in  such  a  growth  as  can 

18 


410 


ORGANIC    CHEMISTRY. 


be  obtained.  Rye,  buckwheat,  and  clover  are  among 
the  plants  best  adapted  to  the  purpose.  Vegetable  mat- 
ter is  thus  added  to  the  soil,  which,  in  its  decay,  hastens 
the  decomposition  of  the  soil  itself. 

What  is  said  1028.    DEFICIENCY  OF  ONE  OR  MORE  CON- 

of  defitien-       sTiTUENTs.  —  The  comparative    exhaustion 

ties  in  partic- 

ular constitu-  of  some  one  or  more  of  the  constituents 
of  the  soil,  is  a  much  more  frequent  oc- 
currence. It  is  commonly  the  result  of  the  cultiva- 
tion of  the  same  crop  during  many  successive  seasons, 
and  the  consequent  reduction  of  those  materials  which 
the  particular  plant  requires  in  largest  proportion.  De- 
terioration of  soils  from  this  cause,  is  repaired  by  an 
artificial  supply  of  the  failing  ingredients.  It  is  more 
wisely  guarded  against  by  such  a  rotation  of  crops  as 
shall  make  different  demands  upon  the  soil  in  succes- 
sive years. 

What  is  said  1029.      MAINTENANCE     OF     FERTILITY.  - 

°f  the  e/ect  °f  The  effect  of  decomposing  animal  matters 

decomposing 

animal  matter    on  the  soil,  has  been  already  considered. 
the  soil  ?  return  the  very  material  which  was 


abstracted  from  the  soil,  with  the  addition  of  nitro- 
genous matter,  originally  derived  from  the  air  by  the 
growing  plant.  In  an  enlightened  system  of  rural 
economy,  the  production  of  these  materials  in  large 
quantity  and  their  careful  preservation,  is  therefore  an 
object  of  paramount  importance.  The  addition  of 
gypsum  or  dilute  sulphuric  acid  to  fermenting  ma- 
nures, is  of  great  advantage  in  retaining  their  ammonia 
in  the  form  of  sulphate,  and  preventing  its  escape  into 
the  air.  When  additional  ammonia  is  required,  it  is 


411 

most  cheaply  obtained  in  the  form  of  guano.  The 
phosphates,  whose  quantity  may  be  often  increased 
with  advantage,  are  best  supplied  in  the  form  of  "  super- 
phosphate of  lime."  Other  materials  are  less  frequently 
required.  For  further  information  on  the  subject  of 
the  present  section,  the  student  is  referred  to  works 
which  treat  especially  of  Agricultural  Chemistry. 

1030.   "  SUPERPHOSPHATE   OF   LIME." — 

What  is  said 

of  superphos-  1  he  method  employed  in  the  manufacture 
phateofiime?  of  «  superphosphate  of  lime,"  has  been  al- 
ready given  in  the  chapter  on  Salts.  As  in  the  case 
of  guano,  its  agricultural  value  depends  on  actual  or 
potential  ammonia,  and  phosphate  of  lime.  In  propor- 
tion as  the  phosphoric  acid  is  in  a  soluble  form,  the 
value  is  much  increased.  Additional  information  on 
this  subject  is  given  in  the  Appendix. 


ANIMAL    NUTRITION.  41.3 

.'.  ••--^-. •«,.-!-,  ..'». 

CHAPTER  III. 


ANIMAL  CHEMISTRY. 

ANIMAL  NUTRITION. 
1031.  RELATIONS  OF  ANIMAL  AND  VEGE- 

How  is  the 

life  of  am-  TABLE  LIFE.  —  The  life  of  animals  is  sus- 
mah  sustain.  tained  by  the  consumption  of  material 
compounded  and  prepared  by  the  plant, 
and  converted  into  its  own  substance,  out  of  the  mate- 
rials of  the  earth  and  air.  This  is  virtually  true  even 
of  the  carniverous  species,  for  the  animals  on  which 
they  feed  have  derived  their  support  from  the  vege- 
table world.  When  they  yield  their  own  flesh  as  food, 
it  is  only  a  changed  vegetable  matter  which  they  thus 
supply.  All  animal  matter  may  therefore  be  regarded 
as  vegetable  matter,  more  or  less  modified,  or  entirely 
transformed  by  the  processes  of  the  animal  body. 

1032.  FORMATION  OF  BLOOD.  —  The  blood 


tion  of  the        material    required   for   animal    growth   is 

blood?  -  ,  .        *        .  mi  •  •  V 

floated  to  its  destination.  This  complex 
fluid  will  therefore  first  engage  our  attention.  The 
food  having  been  ground  up  by  the  teeth,  and  moist- 
ened by  the  saliva,  is  conveyed  to  the  stomach,  and 


414 


ORGANIC    CHEMISTRY. 


submitted  to  the  action  of  the  gastric  juice.  Here  it  is 
converted  into  a  uniform  greyish  semi-fluid  mass,  called 
chyme.  The  chyme  is  pushed  forward  by  sponta- 
neous contraction  of  the  stomach.  It  yields  its  nutri- 
tious matter,  in  the  form  of  a  milky  liquid  called 
chyle,  to  minute  absorbent  vessels,  distributed  upon 
the  surface  of  the  intestines.  Through  these  absorb- 
ent vessels  it  passes  into  the  general  circulation,  and 
is  converted  into  blood. 

What  are  the  1033.     TRANSFORMATION    OF    THE     FOOD. 

offices  of  the      The  transformation  of  the  nutritious  por- 

qastricand  .  ,,     .  .  .  ,     T       .         ~,          1 

pancreatic  tion  of  the  chyme  into  chyle,  is  effected, 
juices?  jn  partj  j^  the  gastric  juice,  and  in  part  by 

the  secretion  of  the  pancreas.  The  latter  organ  lies 
back  of  the  right  end  of  the  stomach,  and  pours  its 
secretions  into  the  duodenum,  or  first  of  the  small  in- 
testines. The  gastric  juice  dissolves  the  protein  com- 
pounds of  the  food,  while  the  secretion  of  the  pan- 
creas transforms  the  sugar  and  starch  of  the  food  into 
grape  sugar.  The  chyle  is  thus  perfected,  and  pre- 
pared to  be  drawn  off  from  the  refuse  portions  of  the 
food.  As  sugar  forms  no  part  of  healthy  blood,  we 
must  suppose  that  it  undergoes  immediate  transforma- 
tion with  fat  or  other  material,  as  soon  as  it  enters  the 
circulation.  The  office  of  the  bile  which  is  secreted 
by  the  liver,  and  poured  into  the  intestines,  is  not  tho- 
roughly understood. 

1034.   THE  GASTRIC  JUICE. — The  saliva 

To  what  is  the          .....          .....        -11        *     *  • 

solvent  agency  which  is  mingled  with  the  loocl  in  masti- 
of the  gastric  cation  has  an  effect  similar  to  that  of  the 

juice  due  ? 

secretion  of  the  pancreas.     Another  of  its 


THE    BLOOD.  415 

probable  agencies  is  to  introduce  air  into  the  stomach,  to 
act  upon  its  lining  membrane  and  produce  from  it  one 
of  the  constituents  of  the  gastric  juice.  The  solvent 
agency  of  this  fluid  is  in  part  owing  to  the  ferment 
thus  formed,  and  in  part  to  the  free  acids  which  it  con- 
tains in  solution.  The  latter  are  phosphoric,  hydro- 
chloric, butyric,  and  lactic  acids,  in  part  free,  and  partly 
in  the  form  of  salts. 

1035.  COMPOSITION    OF   THE    BLOOD. — 

Give  the  com- 

position  of  the  If  fresh  blood  is  beaten  with  a  branched 
blood'  stick,  it  is  separated  into  a  slightly  alka- 

line liquid,  called  the  serum,  a  fibrous  material  called 
fibrine,  and  red  globules,  which  sink,  after  a  time,  to 
the  bottom  of  the  vessel.  The  fibrine  adheres  in  threads 
to  the  stick  with  which  the  operation  is  performed.  It 
is  analogous,  in  composition  and  properties,  to  the  vege- 
table gluten  from  which  it  is  formed.  The  serum  con- 
tains albumen,  and  resembles  the  white  of  egg.  The 
globules  are  also  principally  albumen,  with  a  small 
proportion  of  a  red  coloring  matter  called  hematosine. 
Albumen  and  fibrine  both  contain  phosphate  of  lime  or 
bone  earth.  The  serum  contains,  also,  certain  salts, 
and  a  small  proportion  of  fat.  All  of  these  substances 
together  form  but  about  one-fifth  of  the  blood ;  the 
remaining  four-fifths  are  water.  When  blood  is  left  to 
stand,  after  being  drawn  from  the  body,  the  fibrine  coag- 
ulates spontaneously,  entangling  and  taking  with  it  the 
red  globules,  and  thus  separating  them  from  the  serum. 

1036.  ANIMAL  NUTRITION. — It  is  evident 

What  niateri-      /.  ,  -, .  1,1  -u 

ah  arc.  found  irom  the  preceding  paragraph  that  much 
ready  formed  Of  the  materjai  required  to  build  up  the 

in  the  blood  ?  r 

body,  is  found  ready  formed  in  the  blood. 


416  ORGANIC    CHEMISTRY. 

It  has  been  transferred  to  it  from  the  vegetable  world 
without  material  change  in  composition.  Thus  the 
fibre  which  is  required  for  muscle  and  fat  to  fill  out  the 
tissues,  require  only  to  be  built  into  their  places  in  the 
animal  frame,  as  a  mason  lays  up  a  wall  from  materials 
provided  to  his  hand.  For  the  production  of  other 
animal  substances,  essential  changes  are  required.  The 
power  of  selection  and  appropriation  of  the  proper  ma- 
terials for  every  organ  and  every  secretion,  is  found  to 
reside  in  innumerable  minute  cells,  which  are  distributed 
in  every  part  of  the  body,  and  are  endowed  with  pecu- 
liar powers,  according  to  the  offices  they  are  designed 
to  fulfill. 


BONES,  FLESH,  &c. 

1037.  BONES. — Bones  consist  of  earthy 

What  is  the  J 

composition  of  matter,  and  a  cartilagenous  material  com- 
itThLnr  iS  monly  known  as  gelatine.  The  bone 
earth,  or  mineral  matter,  is  principally 
phosphate  of  lime,  arid  forms  in  mammiferous  animals 
about  two-thirds  of  the  whole  weight.  The  remaining 
third  is  cartilage.  Either  of  these  constituents  may 
be  removed  from  the  bone  without  effecting  its  shape. 
By  removal  of  the  cartilage,  a  brittle,  earthy  frame- 
work remains.  By  removal  of  the  earthy  material,  a 
perfectly  flexible  mass  is  obtained,  of  a  form  entirely 
similar  to  that  of  the  original  bone.  The  first  change 
may  be  effected  by  long  digestion  in  dilute  muriatic  acid, 
and  the  latter  by  fire.  If  in  the  second  process  the  car- 
tilaginous matter  is  not  entirely  consumed,  bone  black 


FLESH.  417 

or  animal  charcoal  is  produced,  the  uses  of  which 
have  been  already  described. 

Of  what  does  1038.  FLESH. — Lean  flesh  or  animal 
flesh  consist  ?  muscle  is  composed  of  fibrine,  penetrated 
by  a  liquid  which  forms  four-fifths  of  the  whole,  and  is 
called  flesh  fluid,  or  juice  of  the  flesh.  It  contains  a 
peculiar  organic  acid,  possessing  the  flavor  of  broth, 
crystalline  substances  called  creatine  and  creatinine, 
and  certain  salts.  Being  extracted  by  cold  water  and 
then  heated,  it  forms  a  nourishing  and  highly  flavored 
soup.  Hot  water  coagulates  its  albumen,  and  prevents 
its  escape  from  the  flesh.  Gradual  heating  is  on  this 
ground  to  be  recommended  in  the  preparation  of  soups, 
while  sudden  exposure  to  a  high  temperature,  both  in 
boiling  and  roasting,  yield  more  nutritious  and  highly 
flavored  meats.  The  salts  of  potash  prevail  in  the  flesh 
fluid,  while  those  of  soda  are  more  abundant  in  the 
blood.  Unlike  the  blood,  this  fluid  is  acid  in  its  re- 
action. 

1039.   SKIN,  TENDONS,  LIGAMENTS. — The 

What  is  said 

of  tendons  and  cartilaginous  material  above  mentioned  as 
ligaments  ?  a  const jtuent  of  bones,  is  transformed  by 
boiling  water,  without  change  of  composition,  into 
gelatine  or  glue.  The  skin,  cellular  membrane,  tendons 
and  ligaments  of  the  body  undergo  the  same  change,  and 
yield  the  same  product.  Gelatine  may  even  be  prepared 
from  refuse  leather,  by  first  extracting  the  tannin,  and 
thus  reducing  it  to  the  condition  of  the  original  hide. 
The  tannin  obtained  in  the  process  may  also  be  em- 
ployed for  tanning  new  hides.  Hoofs,  hair,  horn,  and 
feathers,  although  very  similar  substances,  are  not  thus 
affected  by  boiling. 

18* 


418  ORGANIC    CHEMISTY. 

Wliat  isgela-  1040.  GELATINE.  —  Gelatine  is  soluble  in 
tine?  water,  and  yields  a  stiff  jelly  on  cooling 

from  a  hot  solution.  On  this  property  is  based  its  use 
in  the  preparation  of  jellies  for  the  table.  The  com- 
mercial article  employed  for  this  purpose  and  ordinary 
glue  are  essentially  the  same. 

1041.  The   substance  known   as  isin- 

Crive  the  com-         7  .,        -I--I--II-IT  <• 

position  and  glass,  is  the  dried  air  bladder  of  a  species 
°^  sturoeon5  au&  forms  m  its  natural  con- 
dition, a  soluble  gelatine.  Gelatine  contains 
the  four  principal  organic  elements  ;  nitrogen  and  oxy- 
gen being  in  somewhat  larger  proportion  than  in  the 
protein  bodies.  Hoofs,  hair,  and  the  other  substances 
above  mentioned,  contain  sulphur  in  addition.  Gelatine 
is  susceptible,  like  the  protein  bodies,  of  putrefaction, 
and  also  of  exciting  fermentation.  As  starch  is  changed 
into  sugar  by  the  action  of  dilute  sulphuric  acid,  so  by 
the  action  of  oil  of  vitriol,  gelatine  may  be  converted 
into  a  sweet  crystalline  substance,  called  glycocoll  or 
sugar  of  gelatine. 

1042.  HIDES,  TANNING.  —  A  solution  of 

What  chemical 

combination       gelatin  forms,  with  tannin  or  tanmc  acid, 


tan~  a  tenacious  insoluble  precipitate.  The 
tanning  of  leather  depends  on  the  forma- 
tion of  this  insoluble  compound  in  the  hides  which 
are  submitted  to  the  process.  They  are  im- 
mersed for  this  purpose  in  an  infusion  of  oak 
and  hemlock  bark,  until  the  combination  has 
taken  place  throughout  the  whole  thickness. 
They  are  thus  secured  against  putrefaction 
and  converted  into  firm,  elastic  leather.  Hides  may 


FATS.  419 

also  be  preserved  by  soaking  them  in  alum  and  after- 
ward in  oil.  Soft  chamois'  leather  is  prepared  by 
working  the  skin  with  fat  alone. 


FATS. 

1043.  COMPOSITION. — We  have  already 

What  is  said  * 

of  the  consti-  seen  that  there  are  both  acids  and  bases  of 
tutton  of fats?  pureiy  organic  origin,  and  that  these  may 
combine  like  the  similar  compounds  of  inorganic  chem- 
istry, to  form  salts.  The  animal  fats  and  oils  are  mix- 
tures of  such  compounds  in  different  proportions.  The 
principal  of  these  organic  salts  are  stearine,  margarine, 
and  oleine.  Stearine  is  solid,  oleine  fluid,  and  marga- 
rine occupies  a  middle  position  between  the  two.  The 
difference  of  consistence  in  butter,  lard,  and  tallow, 
is  owing  to  varied  proportions  of  these  three  substances 
which  enter  into  their  composition.  Beside  the  fats 
contained  in  other  parts  of  the  body,  the  brain  and 
nerves  of  animals  contain,  with  albumen  and  water, 
certain  peculiar  acids  and  fats. 

1044.  SEPARATION   OF   FATS   IN   OIL. — 

How  may  the  .  IT-  /• 

constituents  of  The  steariiie  and  oleine  of  whale  oil  sep- 
°rated?Cpa'  arate  spontaneously  in  cold  weather.  The 
cold  which  i£  sufficient  to  harden  the  for- 
mer, leaves  the  latter  in  a  fluid  condition.  This  effect 
is  often  observed  in  lamps  during  winter  weather.  The 
case  is  quite  analogous  to  the  separation  of  cider  into 
alcohol  and  water,  by  freezing.  The  water  congeals, 
and  leaves  the  alcohol  fluid.  Both  separations  are  im- 
perfect. As  the  alcohol  produced  by  the  above  process 


420  ORGANIC    CHEMISTRY. 

is  diluted  to  a  large  extent  with  water,  so  the  oleine 
retains  a  considerable  portion  of  stearine  in  solution. 

1045.   SEPARATION  OF  FATS   IN  TALLOW 

How  may  the  .        .       ,       .       ,  f  .      , 

different  fats  AND  LARD. — Stearuie  is  obtained  from  lard 
and  tallow  on  a  similar  principle.  It  har- 
dens on  partially  cooling  the  melted  fat, 
forming  a  mass  from  which  the  fluid  oleine  may  be  sep- 
arated by  pressure.  Stearine  thus  obtained  is  used  in 
the  manufacture  of  candles,  while  the  oleine  forms 
lard  or  tallow  oil.  The  former  has,  of  late  years,  given 
place  to  stearic  acid,  procured  from  the  same  sources, 
by  means  to  be  hereafter  described.  Margarine  may  be 
separated  from  butter  by  similar  heating  and  slow 
cooling.  It  is  regarded  by  some  chemists  as  a  simple 
mixture  of  stearine  and  oleine.  and  not  a  distinct  sub- 
stance. 

1046.  GLYCERINE. —  Glycerine  is  the  base 
cer'me?  How  of  all  the  fatty  salts  which  have  been 
is  it  made?  mentioned.  It  is  a  viscid,  sweetish  liquid 
containing  the  same  elements  as  grape  sugar,  and  in 
nearly  the  same  proportion.  On  removing  the  stearic, 
and  oleic  acids  from  melted  stearine,  or  oleine,  it  re- 
mains in  the  liquid  form.  This  removal  may  be  ef- 
fected by  lime.  The  white  lime  compound  floats 
upon  the  water  which  is  used  in  the  process  while 
glycerine  is  dissolved. 

How  is  stearic  1047.  STEARIC  ACID. — The  compound 
acid  made?  formed  by  lime,  as  described  in  the  last 
paragraph,  if  tallow  has  been  used  in  the  process,  is  a 
mixture  of  oleate  and  stcrate  of  lime.  From  these, 
stearic  and  oleic  acids  are  liberated  by  the  agency  of 


SOAPS.  421 

diluted  oil  of  vitriol.  The  material  floats  on  the  dilute 
acid,  gradually  losing  lime,  and  becoming  transparent 
by  its  action.  Sulphate  of  lime  or  gypsum  is  formed 
at  the  same  time  and  sinks  to  the  bottom  of  the  vessel. 
The  stearic  and  oleic  acids  are  drawn  off  while  yet 
warm,  and  run  into  cubical  moulds.  The  latter  is  sub- 
sequently removed  from  the  mixture  by  gentle  heat 
and  pressure.  The  remaining  stearic  acid  is  then  re- 
melted  and  allowed  to  cool  slowly.  It  is  thus  ob- 
tained in  a  brilliant  white  mass,  of  crystalline  texture, 
with  the  lustre  of  mother  of  pearl.  This  material  is 
principally  employed  in  the  manufacture  of  candles. 
Its  superiority  to  stearine  for  this  purpose,  consists  in 
the  fact  that  it  is  less  softened  by  heat.  The  two  sub- 
stances differ  in  their  melting  point  about  ten  degrees. 
1048.  SOAPS. — Soaps  are  compounds  of 

How  are  pot-  .  '     . 

ash  and  soda      stearic  and  oleic  acids  with  caustic  potash 

~  or  soda'*  They  are  Produced  by  boiling 
fats  with  either  of  the  alkalies,  till  the 
mixture  becomes  nearly  or  quite  transparent.  The 
glycerine  which  is  expelled  from  the  fats  in  the  process, 
remains  mixed  with  the  soap  which  is  produced.  Pot- 
ash soaps  are  soft.  Soda  soaps  may  be  converted  into 
a  floating  coagulum,  and  separated  from  the  water  used 
in  their  preparation  by  means  of  common  salt.  This 
method  is  employed  to  give  them  their  hardness.  The 
action  depends  on  the  insolubility  of  the  soap  in  salt 
water.  Salt  added  to  potash  soap  seems  to  have  the 

*  In  the  ordinary  preparation  for  soap  making,  the  lye  is  made  to 
pass  through  lime  in  the  leach  tub,  that  its  carbonic  acid  may  be  par- 
tially  removed. 


422  ORGANIC    CHEMISTRY. 

same  effect.  But  its  action  in  this  case  is  due  to  a 
double  decomposition,  in  which  a  floating  soda  soap  is 
formed,  chloride  of  potassium  remaining  in  solution. 
Soaps  may  be  also  made  without  the  use  of  water,  by 
combining  oil  or  fat  with  melted  potash. 

1049.  LINIMENTS,  &c. — Soaps  are  soluble 

How  are  trans- 
parent soaps       in  alcohol,  forming   the   tincture    of  soap 

which  is  used  for  bruises.  With  the  ad- 
dition of  camphor,  this  tincture  forms  opo- 
deldoc. Transparency  is  imparted  to  soap  by  the  evap- 
oration of  an  alcoholic  solution  of  the  well  dried  mate- 
rial. Liniments  are  soaps  prepared  from  ammonia  and 
oil  by  the  simple  agitation  of  the  materials. 

1050.     PROPERTIES    OF     SOAPS. — Soaps 

Explain  the 

cleansing  ac-      which   are   prepared,  as   above  seen,   from 

tion  of  soap.  ^  &nd  ^  haye  the  property  Qf  dissol- 
ving more  of  the  same  material.  On  this  property 
their  cleansing  effect  principally  depends.  When  they 
are  dissolved,  a  portion  of  the  alkali  becomes  free  by 
the  substitution  of  water  as  base.  This  free  alkali 
adds  to  the  cleansing  effect,  by  its  own  affinity  for  the 
oils  and  other  organic  matter.  Alkalies  alone  are  not 
equally  effectual ;  they  tend  to  shrink  the  fibre  of  cloth, 
and  thus  protect  it  against  a  perfect  purification.  The 
strength  of  the  tissue  is  at  the  same  time  gradually  im- 
paired. 


MILK,  BUTTER,  &c. 
1051.    MILK. — Milk    is    analogous   to 

What  is  the  .  •        T    i    •       , 

composition  of   blood  in  compositon,  as  is  implied  in  the 
milk?  office  which  it  fulfills  in  the  nutriment  of 


423 

the  young  animal.  But  casein  takes  the  place  of  the 
fibrin  of  the  blood,  and  fat  is  also  found  in  milk,  in 
much  larger  proportion.  This  fluid  also  contains  sugar? 
which  is  peculiar  in  its  character  and  has  therefore 
received  the  name  of  sugar  of  milk.  Butter  is  pro- 
duced by  the  coalescence  of  the  small  particles  of  oil 
which  are  suspended  in  milk,  and  partially  separated  in 
the  cream.  Chemically  considered,  it  is  a  mixture  of 
oleine  and  margarine.  On  partially  cooling  melted 
butter,  the  latter  collects  at  the  bottom  of  the  liquid 
oleine,  which  forms  the  other  constituent ;  a  portion 
at  the  same  time  remains  in  solution.  Beside  the 
above  substance,  butter  contains  phosphates  and  other 
salts,  with  certain  neutral  fats,  from  which  it  derives 
its  flavor. 

1052.  CHEESE. — On  exposure  to  the  air 

Why  is  the  .         •  .        , 

curd  separated  for  a  considerable  time,  the  sugar  contained 
by  exposure?  ^R  mjjj£.  -g  partiaiiy  converted  in  lactic  acid, 

and  the  casein  is  precipitated.  One  reason  of  this  pre- 
cipitation is  to  be  found  in  the  neutralization  of  the 
free  alkali  of  the  milk.  The  casein  having  thus  lost 
its  solvent,  assumes  the  solid  form.  The  coagulation 
of  milk  may  also  be  effected  by  rennet,  which  con- 
sists of  an  infusion  of  the  lining  membrane  of  the 
stomach  of  the  calf.  Its  mode  of  action  is  not  well 
understood. 

1053.    SOLID    MILK. — Milk    may    be 
brought   into  the    solid   form   by  careful 
pared?  evaporation,    with    a   moderate    heat.      It 

must  be  constantly  stirred  during  the  process.  A  ma- 
chine has  been  recently  patented  which  secures  all  of 


424  ORGANIC    CHEMISTRY. 

these  objects.  With  the  addition  of  a  little  soda  and 
gum,  milk  may  be  thus  kept  sweet  in  the  solid  condition 
for  many  months.  The  addition  of  water  is  all  that 
is  necessary  to  reproduce  it  in  its  original  form. 

CHEMICAL  CHANGES  IN  THE  ANIMAL  BODY. 

1054.  Certain  important  changes  which 

What  is  said 

of  changes  in  are  constantly  occurring  in  the  animal  body 
^animal  remain  to  be  considered.  The  body  is 
not  the  same  in  any  two  successive  mo- 
ments of  its  existence.  Every  breath  exhales  a  por- 
tion of  its  substance  into  the  atmosphere,  and  every 
effort,  whether  of  brain  or  muscle,  is  accompanied  by 
some  transformation  in  the  material  of  which  it  is 
composed. 

1055.  CHANGES  IN  THE  BLOOD. — By  com- 

Mention  cer- 
tain changes  paring  the  blood  of  animals  with  their 
in  the  blood?  foodj  it  win  be  evident  that  certain  mate- 
rials have  been  not  only  modified,  but  entirely  trans- 
formed in  its  production.  Starch  and  sugar  are  impor- 
tant constituents  of  the  food,  but.  they  form  no  part  of 
healthy  blood.  They  are  transformed  into  fat  or  other 
material  as  soon  as  they  enter  the  circulation,  and  in 
this  new  form  constitute  the  fuel  from  which  the  heat 
of  the  animal  body  is  derived.  Other  changes  which 
occur  in  the  blood  will  be  mentioned  in  subsecuient 
paragraphs. 

1056.     ANIMAL     HEAT. — The     oxygen 

What  is  the 

source  of  an-  which  is  necessary  for  the  slow  combustion 
imalheat?  Qf  ^  materiai  aDove  mentioned,  is  taken 

into  the   blood  in  the   course   of  its   passage   through 


RESPIRATION.  425 

the  lungs.  It  passes  on  with  them,  through  the  ar- 
teries, into  the  minute  capillary  vessels  which  are 
distributed  throughout  the  body.  In  these  vessels 
their  combination  takes  place,  with  the  same  produc- 
tion of  carbonic  acid  and  evolution  of  heat,  as  if 
the  material  were  burnt  in  air  or  oxygen  gas.  The 
carbonic  acid  thus  formed  is  carried  back  to  the  lungs 
in  the  venous  blood,  and  there  exhaled,  through  the 
thin  membrane  of  the  air  cells,  and  exchanged  for  a 
new  supply  of  oxygen  gas.  In  view  of  the  relations 
of  starch  and  sugar  to  the  process  of  respiration,  as 
above  shown,  they  have  been  termed  the  respiratory 
constituents  of  the  food. 

1057.    RESPIRATION. — In    cold  weather 

What  is  said  .     . 

further  of  res-  a  larger  amount  of  oxygen  is  inhaled  with 
piratwn  ?  every  breath,  in  consequence  of  the  greater 
density  of  the  air.  Respiration  is  also  involuntarily 
hastened,  and  the  blood,  from  the  two  causes  combined, 
becomes  more  thoroughly  impregnated  with  oxygen 
gas.  The  transformation  or  combustion  of  the  respi- 
ratory constituents  of  the  blood,  proceeds  more  rap- 
idly in  consequence,  and  more  internal  heat  is  pro- 
duced to  oppose  the  external  cold.  This  is  one  of  the 
provisions  of  nature  by  which  the  animal  body  is  ena- 
bled to  resist  the  influence  of  the  seasons  and  of  cli- 
mate. Labor  has  the  same  effect  as  cold  in  hastening 
respiration  and  necessitating  a  larger  supply  of  food. 

What  change  1058.    CHANGE  IN  COLOR  OF    THE  BLOOD. 

of  color  does     FrOm  the  fact   that  the   globules  of  the 

the  blood  ex-  ° 

perience  in  the  blood  undergo  a  change  of  color  in  the 
lunss-  lungs,  where  oxygen  is  absorbed,  it  is  pre- 

sumed that  they  serve,  by  absorption  of  the  gas,  as  the 


426  ORGANIC    CHEMISTRY. 

medium  for  its  conveyance  through  the  body.  As 
a  consequence  of  the  changed  color  of  the  globules, 
arterial  blood  is  of  a  bright  scarlet,  while  venous 
blood  is  dark  red.  The  same  change  of  color  which 
takes  place  in  the  lungs,  may  be  readily  produced  by 
agitating  blood  drawn  from  the  veins  with  air  or  ox- 
ygen gas. 

What  is  said  1059.  RELATIONS  OF  FOOD  AND  TEM- 
of  therein-  PERATURE. — In  proportion  as  the  draft  of 

tions  of  food  „  .       .  n  „      . 

and  tempera-  &  furnace  is  increased,  more  fuel  must  be 
tore?  supplied  for  its  combustion.  For  the  same 

reason  more  respiratory  food  must  be  taken  into  the 
system,  in  proportion  as  more  atmospheric  oxygen  is 
inhaled.  The  fact  that  a  larger  quantity  is  required  in 
northern  climates  thus  receives  a  scientific  explanation. 
The  preference  entertained  in  arctic  regions  for  cer- 
tain kinds  of  food,  is  also  accounted  for  by  the  same 
necessity  for  increased  resistance  to  the  external  cold. 
The  train  oil  and  fat  which  the  Greenlander  con- 
sumes with  avidity,  are  a  better  fuel  in  the  animal 
body  than  the  starch  which  form  a  principal  part  of 
the  food  consumed  in  warmer  climates.  The  chemical 
reason  of  this  difference  is  found  in  the  fact,  that 
starch  and  allied  substances  contains  oxygen  in  larger 
proportion.  They  are,  as  it  were,  in  their  natural  con- 
dition, partially  burned  or  oxidized  substances. 

1060.  CHANGE  OF  THE    ANIMAL  TISSUES. 

What  change 

takes  place  in     In   proportion  to  the  muscular  or  nervous 

lhlbodyTf     activity  of  the   animal,  the    substance    of 

the  body  is  disorganized  and  returned  to 

the   blood  from  which  it  was  produced.      From  the 


UREA.  427 

blood  it  is  finally  removed  by  the  kidneys,  principally  in 
the  form  of  urea  and  uric  acid,  and  thrown  off  as  waste 
material  from  the  system.  These  substances,  although 
organic,  may  be  figuratively  regarded  as  the  ashes  of 
the  consumed  muscle  and  other  nitrogenous  constitu- 
ents of  the  body.  A  portion  of  the  carbon  and  hy- 
drogen of  the  animal  organs  has  at  the  same  time  dis- 
appeared, like  the  elements  of  respiratory  food,  in  the 
form  of  water  and  carbonic  acid. 

What  is  1061.    UREA. — Urea,    when "  separated 

said  of  Urea  ?  frOm  its  solution,  is  obtained  as  a  white 
crystalline  solid.  Its  molecule  contains  four  atoms  of 
hydrogen,  to  two  each  of  carbon,  nitrogen,  and  oxygen. 
When  left  in  contact  with  the  mucus  with  which 
it  is  accompanied  in  the  secretion  of  the  kidneys, 
it  is  speedily  converted,  by  combination  with  four 
molecules  of  water,  into  carbonate  of  ammonia.  Urea 
may  also  be  artificially  produced  from  cyanic  acid  arid 
ammonia.  This  cyanate  is  identical  with  urea  in 
composition,  and  is  converted  into  urea  by  solution  in 
water  and  evaporation.  It  was  among  the  first  of 
organic  bodies  artificially  produced.  Uric  acid  con- 
tains the  same  elements  with  a  larger  proportion  of 
oxygen,  and  also  yields  ammonia  by  its  decomposition. 
Besides  the  above  substances,  the  secretion  of  the  kid- 
neys contains  various  soluble  salts,  which  have  formed 
part  of  the  body.  The  insoluble  salts  are  removed 
from  the  system  by  other  means. 

1062.  DISAPPEARANCE  OF  FAT. — STARVA- 

What  is  said 

of  the  disap-     TioN. —  Vv  hen    the    supply    oi    respiratory 

P™™nce  °f      food  is  deficient,  nature   avails   herself  of 

the  fat  previously  stored   in  the   animal 


428  ORGANIC    CHEMISTRY. 

body,  as  fuel  to  sustain  tjhe  animal  heat.  It  is  taken 
up  by  the  blood,  and  burned  in  the  capillary  vessels, 
as  before  described.  This  happens  in  the  case  of  the 
bear  and  other  hybernating  animals.  Lying  dormant 
during  the  winter  season,  their  fat  is  consumed,  and 
they  emerge  lean  from  their  dens  in  the  spring.  Where 
food  is  deficient  and  there  is  no  accumulation  of  fat  to 
supply  its  place,  the  muscle  and  other  portions  of  the 
body  are  consumed,  and  death  by  starvation  is  the  con- 
sequence. 

1063.   REPAIR  OF  THE  TISSUES. — As  fast 

How  are  the 

tissues  repair-  as  the  worn  out  matter  of  the  muscles 
and  other  organs  is  removed,  its  place  is 
supplied  in  the  healthy  body  by  new  material  from  the 
blood.  Through  it,  also,  the  phosphates  of  the  soil 
and  the  vegetable  world  are  transferred  to  the  skeleton 
of  the  animal,  and  in  smaller  proportion  to  other  parts 
of  the  frame.  The  blood  is  itself  renewed  by  the 
materials  of  the  food. 

1064.  VARIETIES  OF  FOOD. — It  is  implied 

Mention  two 

classes  of  in  the  foregoing,  that  the  two  classes  of 
food'  substances  which  enter  into  the  compo- 

sition of  the  food  of  animals,  subserve  very  diiferent 
purposes  in  the  animal  economy.  The  first  class,  of 
which  starch  and  sugar  are  the  principal,  serve,  by  their 
gradual  combustion,  to  sustain  the  animal  heat.  They 
are  included,  as  above  stated,  under  the  general  name 
of  respiratory  food.  The  protein  bodies,  on  the  other 
hand,  all  of  which  contain  nitrogen,  are  appropriated 
in  the  formation  of  blood  and  muscle  ;  they  make  up 
the  sanguineous  or  plastic  food.  In  view  of  the  fact 


FOOD.  429 

that  the  respiratory  food  enters  also,  in  a  changed  form, 
into  the  composition  of  the  blood,  the  former  term 
can  scarcely  be  regarded-  as  distinctive.  The  latter, 
which  designates  the  office  of  the  protein  bodies  in 
furnishing  material  to  build  up  the  organs  of  the  body, 
is  much  to  be  preferred. 

1065.  PROPORTIONS  OF  FOOD. — For   the 

What  is  said  .  ,,.,..,, 

of  the  import-  economical  sustenance  of  animals,  it  is  of 
Proportion  of  imP°rtance  tnat  a  proper  relation  of  quanti- 
thetwo  kinds  ty  should  be  maintained  between  these  two 
varieties  of  food.  Respiratory  food  alone, 
provides  no  material  for  supplying  the  waste  of  the  or- 
ganized tissues.  Plastic  food,  on  the  other  hand,  is  es- 
pecially adapted  to  this  end,  but  is  poor  fuel  for  sus- 
taining the  heat  of  the  body.  Yet  in  lack  of  other 
material,  it  is  diverted  from  its  natural  use,  and  thus 
appropriated  at  great  economical  disadvantage. 

1066.  Nature  teaches  us  something  on 

What  does  na- 
ture teach  on     this  subject,   in  the  composition   of  milk 
this  subject?     amj   tnose    grains    which   constitute   the 

principal  food  of  man.  It  will  be  found  by  reference 
to  the  table  in  the  Appendix,  that  the  quantity  of 
respiratory  matter  in  these  substances,  is  from  three  to 
six  times  greater  than  that  of  the  plastic  material. 
When  the  object  is  to  fatten  an  animal,  the  proportion 
of  respiratory  matter  may  be  considerably  increased 
by  the  use  of  potatoes,  rice,  and  other  farinaceous  food. 
Being  furnished  in  excess,  it  accumulates  in  the  body 
in  the  form  of  fat.  Working  animals,  on  the  other 
hand,  must  be  supplied  with  nitrogenous  or  plastic 


430  ORGANIC    CHEMISTRY. 

food  in  large  proportion.  The  use  of  bacon,  with 
peas,  beans,  and  eggs,  and  many  other  popular  mix- 
tures of  food,  are  accounted  for  on  the  principle  above 
stated.  For  the  development  of  most  of  the  views 
presented  in  this  chapter,  the  world  is  indebted  to  the 
distinguished  Liebig. 


ORGANIC  ANALYSIS 

1067.  ULTIMATE  ANALYSIS.  CARBON  AND 

How  are  car- 
bon and  hy-       HYDROGEN. — The    proportions    of    carbon 

'mined  ?deter~  an(^  hydrogen  in  organic  substances,  is 
ascertained  from  the  quantity  of  carbonic 
acid  and  water  which  they  yield  on  combustion.  The 
combustion  is  effected  in  a  glass  tube,  by  means  of 
oxide  of  copper,  and  the  products  are  collected  by 
means  similar  to  those  described  in  the  process  for  an- 
alyzing the  air. 

1068.  NITROGEN  AND  OXYGEN. — Thepro- 

How  are  nitro-  ....  .  , 

gen  and  oxy-  portion  of  nitrogen  m  an  organic  substance 
gendetermin-  is  usuany  determined  by  the  quantity  of 
ammonia  it  will  yield  by  combination 
with  hydrogen.  This  combination  is  effected  by 
heating  the  organic  substance  with  hydrate  of  potassa 
or  soda.  The  quantity  of  the  ammonia  produced  in 
the  process  is  estimated  by  the  amount  of  acid  it  will 
neutralize.  From  the  weight  of  this  compound,  that 
of  the  nitrogen  it  contains  is  readily  calculated.  The 
amount  of  oxygen  in  an  organic  substance  is  ascer- 
tained by  subtracting  the  total  weight  of  all  the  other 
constituents. 


PROXIMATE     ANALYSIS.  431 

How  are  or-  1069.      PROXIMATE    ANALYSIS. When    it 

ganic  bodies  js  desired  to  separate  organic  bodies  from 
fromlach  each  other,  and  determine  their  relative 
other?  proportion  without  reference  to  their  ele- 

mentary composition,  the  methods  are  analogous  to 
those  of  inorganic  chemistry.  Distillation,  and  the 
analysis  of  the  fats,  which  have  been  already  described, 
may  be  taken  as  examples. 


CIRCULATION  OF  MATTER. 


433 


CHAPTER  III. 


CIRCULATION  OF  MATTER. 


1070.  The  relations  of  the  three  king- 

What  proves       ,.."*'  .         ,      . 

the  relation       doms  of  nature  have  been  already  mciden- 


tally  considered    in  former  parts  of   this 
nature?  work.     It  remains  to   present  the  subject 

in  a  single  view.  It  is  obvious,  at  a  glance,  that  the  soil 
does  not  furnish  all  the  material  which  is  required  for  the 
wants  of  vegetable  life.  The  level  of  our  meadows 
is  not  lowered  by  removal  of  successive  crops,  nor 
does  the  forest  dig  its  own  grave  at  its  roots  as  it  lifts 
its  ponderous  trunks  into  the  air.  The  atmosphere, 
as  well  as  the  soil,  contributes  to  the  increase  of  mass, 
whether  of  wood  or  grain,  and  indirectly  feeds  all 
races  of  animal  existence.  The  relation  of  the  three 
kingdoms  of  nature  is  thus  established. 

1071.    Water  is  one    of  the  principal 

How  does  wa-  . 

ter  serve  in  agents  in  the  system  of  circulation  of 
a/matte?/™  matter>  which  constitutes  the  life  of  the 
globe  we  inhabit.  In  the  fulfillment  of  its 
office,  it  passes  incessantly  from  sky  to  earth,  now 
mingling  with  the  currents  of  the  atmosphere,  and 
anon  with  those  which  form  the  arteries  and  veins 
of  the  great  world  of  waters.  Lifted  into  the  atmos- 

19 


434  ORGANIC    CHEMISTRY. 

phere  by  the  sun,  it  descends  again  in  dew  and  rain, 
corroding  and  dissolving  the  rocks  on  which  it  falls, 
and  distributing  them  widely  over  land  and  sea. 

1072.  It  settles  through  the  stony  crust 

What  distinct        ,     .  .      .  ,        ,      , 

office  does  it  of  the  earth,  into  the  dark  recesses  of  the 
fulfil?  rocks  where  crystals  blossom  out  of  the 

formless  stone,  and  supplies  them  with  the  material 
for  their  wonderful  architecture.  It  penetrates  the 
soil,  and  supplies  the  same  material  to  the  roots  of 
plants  for  the  still  more  wonderful  creations  of  leaf, 
and  fruit,  and  flower.  Again  it  hastens  through 
brooks  and  rivers  on  its  course,  and  pours  its  burden 
into  the  sea,  for  the  use  of  the  innumerable  forms  of 
vegetable  and  animal  life  which  inhabit  its  waters. 
The  coral  insect  builds  up  solid  islands  out  of  the  mat- 
ter it  provides.  Countless  shell-fish  clothe  themselves 
in  the  same  rocky  garments,  and  finally  cast  them  aside, 
to  be  buried  under  the  slime  of  the  sea  and  harden,  in 
the  course  of  ages,  into  stone.  The  water  which  has 
served  these  various  offices,  climbs  anew  into  the 
heavens  upon  the  solar  rays,  and  again  descends  in 
the  rain,  repeating  forever  its  round  of  service  to  the 
earth. 

1073.  The  further  relations  of  the  three 

How  may  the  n  L     ,   . 

further  reia-  kingdoms  of  nature  may  be  presented  in 
fhrll  °king-  a  smgle  picture.  Imagine  a  giant  tree,  the 
doms  be  i'llus-  representative  of  all  the  vegetation  of  the 
earth,  spreading  wide  its  branches  as  a  shel- 
ter for  man  and  beast.  Let  us  suppose  them  to  subsist 
entirely  upon  its  fruit,  and  to  warm  themselves  by  fires 
made  from  its  branches.  The  tree,  through  its  leaves, 


CIRCULATION  OF    MATTER.  435 

draws  its  supply  of  gaseous  food  from  the  atmosphere, 
and  through  its  roots,  its  mineral  sustenance  from  the 
soil.  It  has  purified  the  air  in  the  process,  of  gases 
which  would  become  noxious  by  accumulation,  and 
returned  to  it  the  oxygen  which  is  the  vitalizing  breath 
of  the  animal  world.  The  mingled  material  of  its 
food,  worse  than  worthless  to  animals,  has,  at  the  same 
time,  been  transformed  into  wood  and  fruit,  and  other 
forms  of  vegetable  matter. 

1074.  At  this  point,  without  interruption 

Explain  the         . 

return  of  mat-  m  the  circuit,  commences  the  return  of 
mros°here  "*'  material  to  tne  atmosphere  from  which  it 
was  derived.  Animals  that  feed  upon  the 
fruit  of  the  tree,  already  breathe  much  of  it  back 
again  to  the  air,  while  they  live,  and  the  rest  is  re- 
stored by  their  death  and  subsequent  decay.  Leaves 
that  fall  and  moulder,  and  branches  that  are  burned  as 
fuel,  make  the  same  return  of  the  elements  of  which 
they  are  composed,  to  the  great  reservoirs  of  the  at- 
mosphere and  earth.  And  what  happens  thus  to  leaf 
and  fruit,  happens  also  at  last  to  the  parent  tree  itself. 
One  by  one  its  giant  branches  fall  and  moulder,  and 
melting  again  into  the  air,  add  to  its  inexhaustible 
stores  of  fertility,  and  provide  the  material  for  a  new 
round  in  the  grand  system  of  circulation. 

1075. — What  happens  beneath  the  single 

Illustrate  the 

extent  of  these  tree,  occurs  also  in  every  flower  that  lifts 
relations.  ^  petals  to  the  sun,  and  is  a  thousand 
times  repeated  in  every  forest  upon  the  face  of  the  earth. 
No  limits  of  distance  or  of  size,  restrict  the  mutual  rela- 
tions and  dependencies  of  nature.  The  exhaled  carbon 


436  ORGANIC    CHEMISTRY. 

of  the  polar  bear  feeds  the  lotus  of  Egyptian  plains, 
and  the  breath  of  the  southern  lion  is  redistilled  in  the 
fragrance  of  the  Norwegian  pine.  The  particle  of  mat- 
ter that  once  burned  in  the  fire  of  the  poet's  brain,  and 
floated  with  his  song  upon  the  air,  now  blooms  in  the 
mountain  flower  and  anon  lies  buried  in  its  mould. 

1076.  According  to  the  view  thus  pre- 

What  is  the 

material  sour-  sented,  it  will  be  seen  that  the  sun  is  the 
If  the  ^orlf?  §reat  material  source  of  the  life  of  the  world. 
He  wings  the  vapors  that  rise  from  the  sea, 
and  fall  again  to  make  their  ministering  circuit  in 
the  earth.  The  solar  rays  are  the  agents  also,  in  the 
transformation  of  matter,  which  takes  place  in  every 
leaf  and  blossom,  and  provide  the  animal  kingdom  with 
its  food. 

1077.  No  less  is  the  sun  the  source    of 

Show  how  it  is       , .,     ,  ,  t  •    i      •     -, 

the  source  of     all  the  mechanical  power  which  is  known 

UP°n  the    earth'       The    falling  fl°°d  °f  N1~ 

agara  is  but  the  recoil  of  the  spring  which 
is  bent  in  evaporation  from  the  sea  and  earth.  All 
force  which  is  derived  from  the  fall  of  water,  is 
thus  traceable  to  the  sun,  which  lifted  it  in  the  form  of 
cloud  and  vapor.  The  energies  of  fire  and  steam,  are 
only  other  forms  of  the  force  inherent  in  the  solar  rays, 
originally  exercised  in  the  organization  of  the  vegetable 
matter  which  serves  as  fuel.  Immediately  produced 
by  oxidation,  and  the  heat  which  it  evolves,  they  find 
their  ultimate  source,  as  well  as  their  precise  equivalent, 
in  the  deoxidizing  influence  of  the  solar  rays.  The 
forces  of  the  human  body  are  fed  by  consumption  of 
similar  materials,  and  may  therefore  be  traced  to  the 
same  source. 


CIRCULATION    OF    MATTER.  437 

1078.  Every  planet  that  surrounds  with 

What  further 

influence  has  its  orbit  the  great  centre  of  our  system,  is 
equally  dependent  upon  his  influence. 
Held  in  their  courses  by  his  attraction,  and  encircling 
him  in  ceaseless  revolution,  they  draw  from  the  parent 
orb  the  strength  and  beauty  which  clothes  their 
lesser  spheres.  What  wonder,  that  in  vague  acknowl- 
edgement of  his  influence,  heathen  have  acknowledged 
the  sun  as  their  God,  and  worshipped  at  his  shrine. 
How  natural  that  Christian  nations  should  find  in  his 
life-giving  power,  a  fitting  emblem  of  the  glory  and 
beneficence  of  the  great  Father  of  the  Universe,  by 
whom  all  suns  and  systems,  are,  and  were  created. 


APPENDIX.  439 


APPENDIX, 


IN  this  Appendix  are  included  formulae  descriptive  of  chem- 
ical reactions  of  the  text,  and  other  matter  no  less  important, 
whose  introduction  into  the  text  would  have  interfered  in  a 
measure  with  the  plan  of  the  work. 

The  formulae  constitute  a  precise  statement,  in  the  lan- 
guage of  the  symbolical  nomenclature,  of  the  reactions  al- 
ready described  in  more  general  terms.  It  is  not  to  be 
understood  from  the  formulae  that  the  materials  concerned 
in  any  process  must  always  be  brought  together  in  the  pre- 
cise proportions  indicated  in  the  first  member  of  the  equation. 
One  or  the  other  may  be  in  excess  ;  if  so,  the  excess  is  null,  and 
not  considered  in  the  formula.  The  latter  regards  and  indi- 
cates only  the  relative  quantities  which  are  actually  concerned 
in  each  reaction — the  first  member  having  reference  to  the 
materials  employed,  and  the  latter  to  the  products. 

Interpreted  according  to  the  atomic  theory,  each  formula 
gives  on  the  one  side  of  the  equation,  the  nature  and  rela- 
tive number  of  the  atoms  or  molecules  which  take  part  in 
any  reaction,  and  on  the  other,  the  nature  and  relative  num- 
ber of  those  which  result. 

The  student  will  do  well,  as  an  occasional  exercise,  to  cal- 
culate from  the  formulae  the  relative  quantities  of  materi- 
als required  in  a  reaction,  and  of  products  resulting  from  it 
in  pounds  and  ounces.  A  T  in  the  tables  stand  respectively 
for  acetic  and  tartaric  acids. 


440  APPENDIX. 


§160. 

The  numbers  given  in  the  text  are  only  approximations. 
The  exact  quantities  may  be  readily  calculated  by  the  law 
of  expansion  and  contraction  of  gases,  and  vapors  previously 
given,  taking  the  volume  of  steam  at  212°  (§  232,)  as  a  start- 
ing point. 

§  232. 

According  to  the  most  recent  determination,  by  Regnault, 
the  latent  heat  of  steam  is  966'6°.  According  to  the  same 
experimenter  the  sum  of  the  latent  and  sensible  heat  is  not 
rigorously  constant. 

§  235. 

The  apparatus  commonly  employed  in  the  laboratory  for 
distillation,  consists  of 
a  retort  and  receiver, 
as  represented  in  the 
figure.  In  Liebig's  ap- 
paratus, for  the  same 
purpose,  the  vapors  are 
made  to  pass  from  the 
retort  or  flask  through 
a  long  inclined  tube.  The  latter  is  enclosed  in  a  second  tube, 
which  is  constantly  supplied  with  cold  water.  A  more  per- 
fect condensation  is  thus  effected. 

§248. 

ACTIVE  FORCE  or  THE  GALVANIC  CURRENT. —  The  active 
force  of  the  galvanic  current,  is  directly  as  the  whole  electro- 
motive force  in  operation,  and  inversely  as  the  sum  of  all  the 


APPENDIX.  441 

impediments  to  conduction.  The  above  is  Ohm's  law.  By 
the  electro-motive  force,  is  to  be  understood  the  whole  force 
generated  by  the  chemical  action  in  the  battery.  The  im- 
pediments are  found  in  the  imperfect  conducting  power  of 
the  bodies,  whether  liquid  or  solid,  which  enter  into  the  cir- 
cuit, and  the  resistance  which  the  current  encounters  in 
passing  from  one  to  another. 

§  273.  (1.) 

SMEE'S  BATTERY. — Of  all  the  batteries  in  common  use, 
Smee's,  which  is  represented  in  the  figure, 
is  the  simplest.  It  consists  of  a  plate  of 
silver,  with  plates  of  zinc  hanging  near  it 
on  either  side.  The  two  zinc  plates  com- 
municate  with  each  other  by  a  metallic 
connection,  and  are,  therefore,  but  one 
plate.  It  is  found  best  to  roughen  the 
silver  with  platinum  black.  Smees'  bat-j 
teries  are  commonly  sold  in  this  condition. 
The  clamp  and  bar  are  simply  to  keep  the 
plates  in  place.  Water  acidulated  with 
from  one-seventh  to  one-sixteenth  of  its  bulk  of  oil  of  vitriol, 
is  employed  in  this  battery.  It  is  generally  used  in  plating, 
and  is  recommended  to  the  student  on  account  of  its  cheap- 
ness,  simplicity,  and  efficiency. 

§  273.  (2.) 

GROVES'  BATTERY. — In  Groves'  battery  the  metal  plati- 
num is  used,  instead  of  copper  or  silver.  It  is  placed  by 
itself,  in  a  porous  earthern  cup  containing  nitric  acid.  The 
vessel  is  placed  in  a  larger  one,  containing  zinc  and  sulphuric 
acid.  The  two  acids  mix  to  some  extent  through  the  pores 
of  the  inner  cup,  so  as  to  complete  the  circuit  by  their  con- 
19* 


442  APPENDIX. 

tact.  Without  this  the  battery  could  not  ope- 
rate. The  figure  represents  Groves'  battery, 
with  the  thumb  screws  by  which  the  wires 
are  connected  with  the  platinum  and  zinc. 
The  outer  dark  portion  within  the  cup  is  the 
zinc,  divided  from  top  to  bottom,  that  the  acid 
may  flow  freely,  and  come  into  contact  with 
both  sides. 

§  307. 

THE  ATOMIC  THEORY. — That  combination  takes  place  in 
definite  and  multiple  proportions,  is  directly  proved  by  exper- 
iment. Oxygen,  for  example,  unites  with  hydrogen  in  the 
proportion  of  8,  16,  32  and  40,  to  one  of  the  latter  element, 
and  refuses  to  combine  in  any  other  proportion.  If  matter 
were  infinitely  divisible,  no  reason  can  be  assigned  for  this 
fact.  Each  infinitesimal  portion  of  oxygen  possessing  the 
same  affinities,  we  should  expect  to  find  combination  in  exact 
proportion  to  the  quantity  supplied. 

Dalton's  atomic  theory,  the  truth  of  which  is  assumed  in  the 
text,  affords  a  luminous  explanation  of  the  facts  under  consid- 
eration. According  to  this  theory,  oxygen  combines  with  hy- 
drogen in  no  smaller  proportion  than  that  of  8  to  1,  because 
this  is  the  ratio  of  weight  in  the  least  existent  particles  of  the 
two  substances.  It  combines  in  the  proportion  of  16,  24,  32 
and  40,  by  uniting  2,  3,  4  or  5  of  its  atoms  to  one  of  Hydro- 
gen. It  refuses  to  combine  in  any  intermediate  ratio,  be- 
cause its  atoms  are  indivisible.  The  same  view  of  the  con- 
stitution of  matter  is  essential  to  the  explanation  of  innumer- 
able facts  in  organic  chemistry. 

The  value  of  a  table  of  atomic  weights  does  not  depend  in 
the  least  degree  upon  the  reception  of  the  atomic  theory. 
It  is  a  list  of  combining  proportions,  determined  by  careful 


APPENDIX.  443 

analysis,  and  reduced  to  a  simple  standard  of  comparison. 
Its  truth  is  independent  of  all  theory. 

RELATIONS  OF  ATOMIC  WEIGHT  AND  DENSITY. — The  com- 
parative weight  of  equal  measures  or  masses  of  different  sub- 
stances is  not  necessarily  the  same  as  the  comparative  weight 
of  their  atoms.  The  mass  of  iron,  for  example,  is  heavier, 
while  the  atom  of  iron  is  lighter  than  that  of  potassium.  To 
account  for  the  fact,  we  must  suppose  the  lighter  atoms  of 
iron  so  closely  arranged  that  they  thus  more  than  make  up 
by  their  larger  number,  for  their  inferior  weight.  In  solids 
generally,  there  is  no  correspondence  between  atomic  weight 
and  specific  gravity ;  but  in  the  case  of  many  elements  which 
exist  in  the  gaseous  state,  or  are  capable  of  assuming  it,  the 
correspondence  is  complete,  as  shown  in  the  following  para- 
graph. 

COMBINING  MEASURES  OR  EQUIVALENT  VOLUMES. — A  cubic 
foot  of  nitrogen,  weighs  just  fourteen  times  as  much  as  the 
same  measure  of  hydrogen,  and  the  relation  of  the  atomic 
weight  is  the  same.  In  combining  by  atomic  weights  or 
equivalents,  they  therefore  combine  in  equal  measures. 
Chlorine,  and  the  vapors  of  bromine,  and  iodine,  belong 
to  the  same  class.  Taking  hydrogen  1  as  the  standard, 
their  combining  measures  are  all  1.  In  the  case  of  oxygen 
the  correspondence  referred  to  does  not  exist.  It  is  sixteen 
times  as  Iieavy  as  hydrogen,  while  its  atom  weighs  but  eight 
times  as  much  ;  here  again  we  are  under  the  necessity  of 
supposing  a  closer  arrangement  of  the  atoms.  Those  of 
oxygen  are  not  only  heavier,  but  twice  as  closely  approxi- 
mated. Taking  hydrogen  as  the  standard,  the  combining 
measure  of  oxygen  is  therefore  £.  That  of  phosphorus  arid 
arsenic  is  the  same,  and  that  of  sulphur^-.  In  the  case  of 
most  other  substances  the  ratio  is  not  so  simple. 

In  the  comparison  of  combining  measures  it  is  more 
customary  to  adopt  oxygen  as  the  standard  of  unity.  The 


444  APPENDIX. 

combining  measure  of  hydrogen,  chlorine,  etc.,  becomes 
2,  as  a  consequence,  and  that  of  other  gases  or  vapors  is 
proportionally  changed.  In  the  production  of  compound 
gases,  the  elements  either  suffer  no  condensation  or  experi- 
ence  a  very  simple  change  of  volume.  Thus  hydrochloric 
acid  gas,  formed  by  the  combustion  of  hydrogen  and  chlo- 
rine, possesses  the  united  volumes  of  its  constituents. 

EQUIVALENT  VOLUMES  OF  COMPOUND  GASES. — As  the 
equivalent,  or  combining  proportion  of  a  compound,  is 
equal  to  the  sum  of  the  equivalents  of  its  constituents,  it 
follows  that  the  combining  measure  of  hydrochloric  acid, 
is  equal  to  the  sum  of  the  combining  measures  of  hydro- 
gen and  chlorine,  2+2  =  4.  Ammonia  is  formed  by  the 
union  of  three  volumes  of  hydrogen,  and  one  of  nitrogen. 
Condensation  takes  place  to  the  amount  of  £  of  the  whole 
volume  of  their  mixed  gases.  The  combining  measure  is 
therefore  equal  to  the  sum  of  the  combining  measures  of  the 
constituents  divided  by  2.  The  sum  of  the  combining 
measures  is  8.  8-7-2=4.  Steam  is  composed  of  one  com- 
bining measure  (two  volumes)  of  hydrogen,  united  with 
one  combining  measure  or  volume  of  oxygen,  and  condensed 
to  two  volumes  in  combination.  Its  combining  measure  is 
therefore  2.  The  above  instances  may  serve  as  examples 
of  the  interesting  relations  of  atomic  weights,  specific  quan- 
tity, and  combining  measures. 

CALCULATION  OP  SPECIFIC  GRAVITY. — The  density  or  spe- 
cific gravity  of  a  compound  vapor  or  gas  of  known  propor- 
tional composition,  may  be  readily  calculated  from  that  of 
its  constituents,  supposing  the  amount  of  condensation  which 
takes  place  in  their  combination  to  be  known.  The  results 
thus  obtained,  are  more  accurate  than  any  results  of  experi- 
ment. In  like  manner  the  proportional  composition  of  a 
compound  may  be  calculated  from  a  knowledge  of  its  ele- 
ments and  density.  The  density  of  the  vapor  of  carbon  and 


APPENDIX.  445 

other  solids  which  are  not  known  in  the  gaseous  form,  may 
be  calculated  from  the  density  of  their  compounds  with  ele- 
mentary gases  of  known  density.  That  of  carbon,  for  ex- 
ample, may  be  deduced  from  that  of  carbonic  acid.  The 
calculation  involves  an  assumption  as  to  the  equivalent  vol- 
ume of  carbon.  Assuming  it  to  be  the  same  as  that  of  hy- 
drogen, the  density  of  carbon  vapor  is  423 '4.  If  its  equiva- 
lent volume  is  the  same  as  that  of  oxygen  or  £  that  of  hydro- 
gen, the  density  is  doubled. 

ATOMIC  VOLUMES. — It  is  obvious  that  the  number  of  atoms 
of  a  given  weight  in  any  mass,  must  be  in  proportion  to  the 
density  of  the  mass.  The  size  of  the  same  atoms  must  be 
less  in  the  same  proportion.  The  atomic  volume  of  any 
substance  is  therefore  obtained  by  dividing  the  atomic 
weight  by  the  density  or  specific  gravity  of  the  body.  The 
subject  of  atomic  volumes  has  important  relations  to  the 
science  of  crystallography.  In  comparing  atomic  volumes 
it  is  assumed  that  the  space  which  a  body  occupies  is  com- 
pletely filled  by  the  atoms,  without  intervening  space. 

ATOMIC  HEAT. — The  numbers  28,  32,  103,  represent,  in 
the  order  in  which  they  are  given,  the  atomic  weights  of 
iron,  copper,  and  lead.  It  is  a  remarkable  fact  that  if  the 
three  metals  be  taken  in  these  relative  proportions,  it  will 
require  the  same  expenditure  of  heat  to  make  them  equally 
hot.  103  pounds  pounds  of  lead  can  be  heated  up  to  212,° 
for  example,  by  burning  the  same  amount  of  alcohol  which 
will  heat  32  pounds  of  copper,  or  28  Ibs.  of  iron,  to  the  same 
degree.  Most  other  metals,  and  the  non-metallic  element, 
sulphur,  come  into  the  same  class,  or  in  other  words, 
have  the  same  atomic  heat.  The  atomic  heat  of  arse- 
nic and  silver  is  double  that  of  the  elements  above  men- 
tioned.  Other  elements  are  different  in  this  respect,  but 
commonly  by  some  simple  ratio  of  difference.  The  cor- 
respondence is  never  absolute,  but  so  close  as  to  have  lead 


446 


AXPENDIX. 


many  chemists  to  attribute  the  variations  to  errors  of  exper- 
iment, and  to  regard  the  law  of  correspondence  of  atomic 
weights  as  universal. 

§  313. 

CALCULATION  OF  FORMULAE. — The  student  interested  in 
the  subject  will  readily  devise  for  himself  the  reverse  pro- 
cess of  calculating  formulae  from  the  per  centage  results  of 
analysis.  The  formulae  obtained  must  obviously  be  such, 
that  if  reconverted  into  per  cents,  the  numbers  obtained  will 
agree  very  nearly  with  the  results  of  analysis.  There  may 
sometimes  be  a  doubt  whether  the  simplest  formula  which 
will  express  the  composition,  or  some  multiple  of  it  is  the 
true  one.  This  can  only  be  decided  by  the  analysis  of  one 
of  the  compounds  of  the  substance  in  which  the  formula  of 
the  second  constituent  is  established. 

The  reasoning  will  be  best  illustrated  by  an  example.  It 
being  assumed  that  neutral  salts  contain  one  equivalent  of 
base  to  one  of  acid,  the  analysis  of  the  neutral  sulphate  of 
potassa  would  establish  the  formula  for  sulphuric  acid,  SO, 
instead  of  SaOe.  KO,SO3  would  express  correctly  the  com- 
position of  the  salt,  while  the  substitution  of  SsOe  for  SsOa 
in  the  same  formula,  would  give  a  double  proportion  of  acid. 

§  323. 

When  the  same  element  unites  with  oxygen  in  different 
proportions  to  form  different  acids,  these  are  distinguished 
by  prefixes  and  terminations,  which  indicate  the  order  in 
which  they  stand  to  each  other,  with  respect  to  the  quantity 
of  oxygen. 

The  first  acid  of  such  a  series  discovered,  generally  receives 
the  termination  "  ic."  Chloric  acid  may  serve  as  an  exam- 
pie.  Another  acid  compound  of  chlorine  since  discovered, 


"  IlvS'l^' 

^* 

APPENDIX.  447 

and  containing  more  oxygen,  is  called  hyperchloric,  signify- 
ing higher  than  chloric.  The  other  names  of  the  list  indi- 
cate, by  their  prefixes  and  terminations,  the  order  of  oxy- 
geriation  of  the  several  acids.  The  same  means  of  distinc- 
tion are  employed  in  other  series. 

Hypochlorous  acid,  -         -        -»Vv     CIO. 

Chlorous  acid,       ''•"       -        :V      -         -         ClOa. 

Hypochloric  acid,  (peroxide  of  chlorine,)      C1O4. 

Chloric  acid,  'lTi-;H  ClOs. 

Hyperchloric  acid,         ...      •  *vr  <     ClOr. 


§332.  KO,C1O5=KC1+6O. 

§334. 

§338. 

§340.  C+2O=CO2. 

§354.  2HCl+MnOa=2HO+MnCl+Cl. 

§355.  (CaCl+CaO,ClO)+2SO3=2(CaO,SO3)+2Cl. 

§358.  Sb+5Cl=SbCls. 

§  362. 

It  will  be  observed,  on  comparing  §  362  with  those  which 
precede,  that  chlorine  sometimes  expels  oxygen,  and  is 
sometimes  expelled  by  it.  In  relation  to  the  apparent  in- 
consistency of  these  facts,  litrle  more  can  be  said  than  that 
chemical  affinities  are  modified  by  circumstances,  the  action 
of  which  is  not  perfectly  understood. 

§365.  HO+C1-HC1+O. 

I  375.  NaI+2SO3+MnO2=NaO3SO3+MnO,SO3+I 

§384.  S+2O=SOa. 

§400.  Zn+HO,SO3  =  ZnO,  SOs+H. 

§408.  Cu+2SO3=CuO,  SOa 


448  APPENDIX. 

§  411. 

IODIDE  OP  NITROGEN. — Iodide  of  Nitrogen,  a  very  explo- 
sive compound,  is  formed  when  an  alcoholic  solution  of  iodine 
is  added  to  aqua  ammonia.  It  precipitates  in  the  form  of  a 
black  powder.  The  precipitate  should  be  thrown  upon  a 
filter,  washed,  and  while  still  moist,  divided  into  small  por- 
tions for  the  purpose  of  experiment.  When  dry  it  explodes 
violently  by  simple  touch,  and  sometimes  even  spontaneously. 

CHLORIDE  OF  NITROGEN. — Chloride  of  nitrogen  is  a  still 
more  dangerous  compound  than  the  above.  To  prepare  it 
ajar  filled  with  chlorine  gas  is  suspended  over  a  solution  of 
sal  ammoniac,  contained  in  a  leaden  saucer.  After  the  lapse 
of  a  few  hours,  an  oily  liquid  forms  and  falls  to  the  bottom 
of  the  solution.  This  is  the  chloride  of  nitrogen.  Mere 
contact  with  a  combustible  material,  such  as  fat,  oil,  phos- 
phorus, &c.,  is  sufficient  to  cause  its  explosion.  •  A  single 
drop  of  the  liquid  explodes  so  violently  as  to  shatter  to  pieces 
any  earthen  or  glass  vessel  upon  which  the  explosion  takes 
place.  The  preparation  of  this  compound  cannot  be  recom- 
mended ;  in  the  hands  of  the  ablest  experimenters  it  has 
been  the  occasion  of  the  most  dangerous  accidents. 

§413.  P+5O=POs. 

§  424.  KO,  N05  +HO,  S03=KO,  SCh+HO,  NO5. 

§425.  3Cu+4N05=3(CuO,  NO5)+NO2. 

§426.  NO2+2O=NO4. 

§428.  3Sn+2NO5=3SnO3+2NO3. 

§430.  3P+5NO5=3PO5+5NO2. 

§433.  5C+PO5=5CO+P. 

§  446.  AsCls  +6Zn  +  6(HO,  SQ3)  =  6(ZnO,  SOs  + 

3HCl+AsH3. 
§464.  C+2O=CO2. 
§465.  HCl+CaO,CO2:=HO+CaCl+CO2. 


APPENDIX.  449 


§478.  C 

§480.  CaOs,  HO+SO3=HOSO3+CO2+CO. 

§490.  Zn-{-SO3+HO2=ZnO,  SO3+H. 

§492.  3Fe+4HO=Fe3O4+4H. 

§496.  H+O=HO. 

§501.  Na+HO=NaO+H. 

§519.  H+C1=HC1. 

§521.  HO,SOa+NaCl=NaO,  SOs+HCl. 

§530.  SiO3+3HF=3HO+SiF3. 

§537.  N+3H=NH3. 

§539.  CaO+NH4Cl=HO+CaCl+NH3. 

§543.  NH3+HC1=NH4C1. 

§546.  KO+3HO+2P=KO,PO3+PH3. 

§  553.  2SO3+C4H5O2=2(HO,  SO3)+C4H4. 

§577.  2C+KO,CO2=3CO+K. 

§585.  Na+NH4Cl  +  Hg 

§626.  Sb+5Cl=SbCl5. 


§  680. 

The  other  elements  not  mentioned  in  the  text  are  glucinum, 
cadmium,  cerium,  colnmbium  or  tantalum,  didymium,  erbi- 
um, indium,  lanthanum,  molybdenum,  niobium,  norium, 
osmium,  palladium,  pelopium,  rhodinm,  ruthenium,  seleni- 
um. tellurium,  terbium,  thorium,  titanium,  tungsten  or  wol- 
framium,  vanadium,  ytrium,  and  zirconium.  With  the  ex- 
ception of  selenium  and  tellurium,  which  are  analogous  in 
their  properties  to  sulphur,  they  may  be  classed  with  the 
metals.  They  are  of  rare  occurrence,  and  may  be  regarded 
as  sustaining  the  same  relation  to  the  other  elements  as  do 
the  asteroids  and  satellites  to  the  more  important  members 
of  the  solar  system. 

§646.  Zn+PbO,  A=ZnO,  A+Pb. 
§665.  NaCl+AgO,  NO5=NaO, 


450  APPENDIX. 


§685. 

NEUTRAL,  ACID,  AND  BASIC  SALTS.  —  In  general,  salts  con- 
taining  an  equivalent  of  base  to  an  equivalent  of  acid  are 
called  neutral.  The  composition  fixes  the  name,  whether  ex- 
actly  neutral  to  the  taste  and  in  their  action  or  vegetable 
colors,  or  not.  Salts  containing  more  acid  in  proportion 
are  called  super-salts  or  acid  salts,  and  those  containing 
mere  base,  sub-salts  or  basic  salts. 

There  are  two  exceptions  to  the  above  rules.  The  first 
is  that  of  certain  classes  of  acids  which  have  double  and 
treble  neutralizing  power,  and  require,  therefore,  the  first  two 
atoms,  and  the  latter  three  atoms  of  base,  to  make  them 
neutral  salts.  Such  acids  are  bibasic  and  tribasic,  in  contra. 
distinction  from  the  mono-basic  or  ordinary  salts.  Phospho- 
ric acid  is  one  of  the  latter  class  of  tribasic  acids,  and  the 
neutral  phosphates  have  therefore  three  atoms  of  base  and 
is  called  a  tribasic  phosphate.  Phosphates  containing  more 
acid  or  base  than  their  proportion,  are  acid  or  basic  accord- 

ing1 y- 

The  second  exception  is  that  of  salts  or  bases  which  con- 
tain  more  than  one  atom  of  oxygen  to  an  atom  of  metal. 
In  proportion  as  they  contain  more,  they  neutralize  more  acid. 
Alumina  or  oxide  of  aluminium,  for  example,  contains  three 
atoms  of  oxygen.  Its  neutral  sulphate,  therefore,  is  a  salt 
containining  3  atoms  of  acid.  A  salt  of  aluminium  containing 
more  or  less  than  their  proportion,  is  acid  or  basic  accord. 


DOUBLE  SALTS.  —  There  are  also  double  salts  or  compounds 
of  salts  with  each  other.  They  are  generally  of  the  same 
acid.  Thus  alum  is  a  double  sulphate  of  potassa  and  alu- 
mina and  the  bisulphate  of  potassa  may  be  regared  as  a 
double  sulphate  of  potassa  and  water.  Such  double  salts 


APPENDIX.  451 

are  not  mere  mixtures.  They  have  their  own  crystalline 
form,  and  each  particle  of  their  crystals  contanis  all  the  ele- 
ments of  both. 

BINARY  THEORY  OP  SALTS. — Sulphate  of  potassa,  and 
other  similar  salts,  are  commonly  regarded  as  ternary  com- 
pounds.  But  many  chemists  are  of  the  opinion  that  they 
are  constituted  after  the  plan  of  the  binary  salts,  and  their 
acids  on  the  plan  of  a  hydrogen  acid.  They  would  write 
sulphuric  acid,  SO4,H,  instead  of  HO,SOs,  thus  indicating 
that  the  hydrated  acid  is  composed  of  the  radical,  S(X  (a 
compound  playing  the  part  of  an  element,)  with  hydrogen. 
Sulphate  of  potassa  would,  according  to  this  view,  be  writ- 
ten K,SO4,  instead  of  KO,SO3.  The  acid  and  salt  are  thus 
represented  as  analogous  in  constitution  to  a  hydracid  and 
a  binary  salt;  thus,  (SO4)H  corresponds  with  C1H,  and 
K(SO4)  with  KC1.  The  advantage  of  this  view  is  that  it 
makes  but  one  great  class  of  acids,  and  one  of  salts,  associ- 
ating substances  which  are  analogous  in  their  properties. 
Hydrogen  thus  becomes  characteristic  of  an  acid.  This  view 
also  simplifies  the  subject  of  the  production  of  salts  from 
acids,  making  it  to  consist  simply  in  the  replacement  of  the 
hydrogen  of  the  acid  by  a  metal.  Thus  in  the  action  of  sul- 
phuric acid  (HO.SOa)  on  zinc,  sulphate  of  zinc  (ZnO,SOs)  is 
formed  by  the  simple  replacement  of  the  hydrogen  of  the 
acid  by  the  metal  zinc.  As  will  be  seen  more  clearly  in 
the  introduction  to  Organic  Chemistry,  it  is  no  conclusive 
objection  against  the  view,  that  the  radical  SO4  has  not  been 
isolated.  There  is  the  best  reason  for  believing  in  the  exist- 
ence of  many  such  hypothetical  radicals.  A  similar  objection 
has  indeed  been  urged  against  the  ordinary  view,  according 
to  which  SOs  neutralizes  potassa  in  the  sulphate  of  this  base. 
The  objection  lies  in  the  fact  that  anhydrous  sulphuric  acid 
is  not  possessed  of  acid  properties,  and  can  therefore  be 
scarcely  regarded  as  an  acid,  in  its  anhydrous  condition. 


452 


APPENDIX. 


§717.  CaO,  HO+KO,  CO2=CaO,  COa+KOHO. 
§725.  NH3+HO,SO3=NH4O,  SOs. 
§726.  CaO,  CO2=CO2+CaO. 
§  727.  CaO+HO=CaO,  HO. 
§741.  HCl+NaO=HO+NaCL 
§742.  NaCl+AgO,  NO5=NaO,  NO^+AgCl. 
§748.  (CaCl+CaO,ClO)+2CO2=2(CaO,  CO«)+2C1. 
§750.  2CaO+2Cl=(CaCl+CaO,  CIO). 
§751.  3C+3Cl-fAl2O3=3CO+Al2Cl3. 
§760.  HO,  SO3+CaF=CaO,  SOs+HF. 
§762.  PbO,  A+HS=HO,  A+PbS. 
§  769.  NaO+SO3=NaO,  SO.     Vide  §400. 
§770.  (CaO,  SO3+2HO)=2HO-fCaO,  SOs. 
§772.  2HO+CuO,  SOs  =  (CaO,  SOs+2HO). 
§774.  HO,  SO3+NaCl=HCl+NaO,  80s. 
§775.  Glauber's  Salt=(NaO,  SOs  +  lOHO). 
§777.  Alum=(KO,  SOa+AlaOa,  3SO+24HO). 
§778.  (KO,  SOa  +  AlaOs,  3SOs+24HO)=24HO  + 
(KO,  SOs+AhOs,  3SOs). 

c77Q  (ChromeAlum=(KO,SO3+Cr2O3,3SO3+24HO. 
'<  Ammonia  Alum=(NH40,  SOa+AlaOs,  3S03+24HO). 
f Sulphate  of  Zinc  =(ZnO,  SOa+7HO). 
§780.-!  Sulphate  of  Copper^  (CuO,  SOs+5HO). 

[Sulphate  of  Iron=(FeO,  SO3+7HO). 
§783.  Nitrate  of  Potash  (Nitre) =KO,  NO5. 
§784.  CaO,NO5+KO,CO2=CaO,CO2+KO,  NO5. 
§786.  NH40,  N05=4HO+2NO. 
§787.  S+KO,  NO7+3C=KS  +  N+3CO2. 
§789.  Nitrate  of  Silver  (Lunar  Caustic)=AgO,  NO*. 
§  790.  Nitrate  of  Soda^NaO,  NO*. 
§792.  KO,  CO2+CaO,  NO5=KO,  NO5+CaO,CO2. 
§795.  CaO,  CO3+NaS=CaS+NaO,  C02. 
§  797.  Sesqui-carbonate  of  Ammoma=2NH40, 3CO2. 


APPENDIX.  453 

§804.  CaO+C02=CaO,  CO*. 

§  809.  (2NaO,  HO,  P05  +  24HO)  +  3(AgO,  NO  5  = 
2(NaO,NO5)  +  HO,NO5+24HO+3AgO,PO5. 
§  824.  Biborate  of  Soda=(NaO,  2BO3  +  10HO). 
§  828.  Chromate  of  Lead  (Chrome  yellow)  =  PbO,  CrO  3  . 
§829.  KO,  C02  +  2(PbO,  Cr03)=KO,  Cr03+CO2  + 
2PbO,  CrOs. 

§  830. 

Commercial  chrome  green  is  a  mixture  of  Prussian  blue 
and  chrome  yellow. 

§833.  3(KO,  MnO3)+2S03=2(KO,  S03)+MnO2-f 

KO,  Mn2O7. 

§  845.  4NO5+3Ag+Au=3(AgO,  NOs)+NO2+Au. 
§  846.  3NH4O  +  CaO,  NO5  +  A12Q3,  3NO5  = 

3(NH4O,  NO5)+CaO,NO5+Al2O3. 
§  847.  CuO,  NO  5  +  AgO,  NO5  +  HC1  =  CuO,  NO  5  + 

HO,  NO«+AgCl. 

§877.  Woody  Fibre  =  CiaHioOio. 
§890.  Kreosote==Ci4H802. 


Carbazotic 

§894.  Gun  Cotton  (Pyroxalme)=Ci2H808,  4NOs.  ? 
§898.  CJ2HioOio+4HO=Ci2Hi 
§900.  Starch=Ci2HioOio. 
§904.  Ci2HioOio+4HO=Ci2Hi 
§907.  Grape  Sugar=Ci2Hi4Oi4. 
§908.  Cane  Sugar=CiaHnOii. 
§913.  (Ci2Hi2 
4CO2. 

§914.  Alcohol=C4HeOa. 
§917.  C4 


454 


APPENDIX. 


§  919. 


FULMINATES. — This  name  has  been  given  to  a  class  of 
highly  explosive  salts,  obtained  by  the  action  of  alcohol 
upon  certain  nitrates.  The  most  important  are  the  fulmi- 
nates of  mercury  and  silver.  Fulminating  mercury  is  pre- 
pared by  dissolving  1  part  of  mercury  in  12  parts  of  nitric 
acid,  sp.  grav.  1.36,  and  subsequently  adding  11  parts  of  80 
per  cent,  alcohol.  Upon  warming  the  mixture  a  compli- 
cated reaction  takes  place,  dense  white  vapors  are  given  off, 
and  the  fulminate  is  thrown  down  as  a  crystalline  powder. 
This  is  to  be  washed  with  cold  water  and  afterwards  dried 
at  a  moderate  temperature.  This  salt  explodes  violently  by 
heat,  friction,  or  percussion,  and  sometimes  even  without 
any  apparent  cause.  It  is  largely  employed  in  the  manufac- 
ture of  percussion  caps,  torpedoes,  &c.,  &c.  Fulminating 
silver  detonates  still  more  violently  than  the  mercury  salt. 
By  friction  with  a  hard  body,  it  explodes  even  under  water. 
It  is  prepared  as  above,  using  10  parts  of  nitric  acid  and 
20  parts  of  alcohol.  Too  much  caution  cannot  be  observed 
in  manipulating  with  these  highly  dangerous  compounds. 
They  should  be  prepared  only  in  quantities  of  a  few  grains. 
Fulminate  of  Silver=2AgO,  CyaOa. 

§927.  Ether=C4H5O. 

Alcohol =C  4  HeO2  or  (C4H5O+HO). 


§928. 

§929. 

§930.  C4H6O2+2S03=2(HO, 

§931. 

§932. 

§933. 

§935.  Chloroform- C 2  HCFs. 

§938.  Tannic  Acid=Ci  8H5O9,  3HO=Qt,  3HO. 


APPENDIX.  455 

§941.  Cyanogen=C2N=Cy.     An  arbitrary  symbol. 
§942.  FeCy,  2KCy+HgCl2=FeCy,2KCl  +  Hg+2Cy. 
§943.  Cyanide  of  Potassium==KC2N=KCy. 
§944.  Prussian  Blue  =  Ci  8N9Fe7  =  Fe4Cfy3. 

fFerrocyanogen=3Cy,  Fe=Cfy. 
§945.j  Ferrocyanide  of  Potassium  =  (3Cy,  Fe+2K)  = 

I     Cfy,2K. 
§  946.  2(3Cy,  Fe  +  2K)  -  K  =  (2(3Cy,  Fe)  +  3K)  = 

2Cfy,  3K. 
§947.  KCy+HO,  SO3=KO,  SOs+HCy. 

fTartaric  Acid=CsH4Oi  o,  2HO=T,  2HO. 

Oxalic  Acid=C2O3,  HO=O,  HO.^ 
.Citric  Acid^CisHsOn,  3HO=Ci,  3HO. 
49>1  Malic  Acid=C8H408,  2HO-M,  2HO. 

Formic  Acid  =C  2  HO  3,  HO. 
LLactic  Acid=C6H5O5,  HO. 

§  975. 

In  the  present  state  of  our  knowledge  in  respect  to  the 
protein  bodies,  we  must  abandon  every  formula  by  which 
their  atomic  constitution  is  said  to  be  expressed.  Generally, 
they  contain  in  100  parts  :  55.16  carbon,  7.05  hydrogen, 
21.81  oxygen,  16.96  nitrogen,  with  £  to  1  per  cent,  sulphur 
and  phosphorus  in  an  unknown  form. 

Morphine^CssHaoNOe. 

C44H23N2O8  or 


|Quinine=C2oHi2N02. 

[Theine  and  Caffeine=Ci  aHi  oN40. 
§993.  Indigo=Ci6H5NO2. 
§  994.  Alizarine  =  C  2  o  H  i  o  O  i  o  . 
§995.  Hematoxyline  —  C4oHi  ?0i  s. 
§1002.   Vide  §994. 


456  APPENDIX. 

§  1003.  (KO,  SOs  +  Cr2O3,  3S03)  +  3KO  =  4(KO; 
SO3)+Cr2O3. 

§  1025. 

MODE     OF     ESTIMATING    THE     VALUE     OP     GUANO,    &C. In 

estimating  the  money  value  of  guano  for  agricultural  pur- 
poses, ammonia  may  be  set  down  at  16  cents  per  pound, 
potash  at  4  cents,  and  phosphoric  acid  at  1£  to  2  cents.  As 
far  as  the  latter  exists  in  a  soluble  form,  its  value  is  doubled. 
Other  substances  are  of  so  little  comparative  value  that  they 
need  not  be  taken  into  the  account.  These  valuations  are 
based,  not  alone  on  their  relative  value  as  fertilizers,  but  on 
the  cost  of  the  different  substances  when  obtained  from  other 
sources.  They  are  somewhat  arbitrary,  but  may  serve  as  a 
means  of  approximate  estimation  of  the  value  of  guano  and 
other  fertilizers. 

As  an  average  of  the  composition  of  thirteen  samples  of 
Peruvian  guano,  Prof.  Way  obtained  the  following  results  : 
ammonia,  17*41  pgr  cent.;  phosphoric  acid,  11-13;  potash, 
3*50.  This  would  seem  to  be  considerably  above  the  or- 
dinary  average.  The  pecuniary  value  of  such  an  article, 
according  to  the  above  valuation,  would  be  $63.00  per  ton, 
of  which  855.60  would  lie  in  the  ammonia.  No  distinc- 
tion is  made  in  the  potential  and  actual  ammonia  of  guano, 
because  the  conversion  of  the  former  into  actual  ammonia, 
takes  place  so  rapidly  in  the  soil.  But  the  potential  ammo- 
nia of  most  nitrogenous  substances,  as  of  clippings  of  hides 
and  other  similar  refuse,  is  to  be  estimated  at  least  25  per 
cent,  lower,  in  view  of  their  comparatively  slow  conversion. 

In  all  analyses  of  concentrated  fertilizers  excepting  guano, 
in  which  the  first  distinction  may  be  neglected,  the  amount 
of  actual  and  potential  ammonia,  of  soluble  and  insoluble 
phosphoric  acid,  and  of  potassa,  should  be  separately  stated. 


APPENDIX.  457 

The  latter  constituent  is,  however,  of  comparatively  little 
importance.  The  farmer  who  purchases  his  artificial  fer- 
tilizers without  a  skillful  and  well  attested  analysis,  is  at  the 
mercy  of  the  ignorant  or  unscrupulous  dealer. 

§  1 046.  Glycerine  =  C  6  H  e  O  c . 

fStearic  Acid^CesHeeOe,  2HO=St,  2HO. 
§1047.<{Margaric  Acid^Cs^ssOs,  HO. 

[Oleic  Acid^CseHssOa,  HO. 

$Urea=C2N2H403. 

I  Uric  Acid=CioN4H305+HO. 


APPENDIX. 


459 


TABLE  L 


TABLE  OF  THB  DISCOVERY  OF  OKRTAEf  ELEMENTS. 


Authors  of  the  discovery. 


Dates. 


Known  to  the  ancients. 


Names  of  Elements. 
Gold,    . 
Silver,     . 
Iron, 
Copper,  . 
Mercury, 
Lead,      . 
Tin,.     . 
Sulphur, 
Carbon, 

Antimony,  .     .     .  Described  by  Basil  "Valentine, 1490 

Bismuth,    .     .     .     Described  by  Agricola, 1530 

Zinc,  .....  First  noted  by  Paracelsus,  ....     16th  centur}r. 

Phosphorus,   .     .     Brand, , 1660 

Arsenic,  .     .     .    )   grant  1733 

Hydrogen,      .     .     Cavendish, 1766 

Chlorine,     .     .    ,  Scheele, 1774 

Oxygen,     .     .     .     Priestly, 1774 

Manganese,      .     .  Gahn  and  Scheele, 1774 

Chromium,.     .     .  Vauquelin, 1797 

Potassium, 
Sodium,  . 

Sir  Humphrey  Davy, 1807 

Calcium, 
Boron,     . 

Iodine,  ....     Courtois, 1811 

Silicon,    ....  Berzelius, 1823 

Bromine,   .     .     .     Ballard, 1826 

Aluminium,      .     .  "Wohler,    . 1828 

Magnesium,    .     .     Bussy, 1829 


460 


APPENDIX. 


TABLE  IL 


ATOMIC    WEIGHTS.* 

Hydrogen=1.00. 


Aluminium 

Al 

13.63 

Lead 

Pb 

103.57 

Antimony 

Sb 

129.00 

Lithium 

Li 

6.64 

Arsenic 

As 

75.00 

Magnesium 

Mg 

12.00 

Barium. 

Ba 

68.59 

Manganese 

Mn 

27.57 

Bismuth 

Bi 

208.00 

Mercury 

Hg 

100.05 

Boron 

B 

11.04 

Nickel 

Ni 

29.55 

Bromine 

Br 

79.97 

Nitrogen 

N 

14.00 

Calcium 

Ca 

20.00 

Oxygen 

O 

8.00 

Carbon 

C 

6.00 

Phosphorus 

P 

31.36 

Chlorine 

Cl 

35.46 

Platinum 

Pt 

98.94 

Chromium 

Cr 

26.78 

Potassium 

K 

39.11 

Cobalt 

Co 

29.49 

Silicon 

Si 

14,81 

Copper 

Cu 

31.68 

Silver 

Ag      . 

107.97 

Fluorine 

Fl 

19.00 

Sodium 

Na 

23.00 

Gold 

An 

196.67 

Strontium 

Sr 

43.67 

Hydrogen 

H 

1.00 

Sulphur 

S 

16.00 

Iodine 

I 

126.88 

Tin 

Sw 

58.82 

Iron 

Fe 

28.00 

Zine 

Zn 

32.53 

*  These  atomic  weights  are  calculated  fro-ni  the  best  and  most  pre- 
cise investigations;  some  of  them  have  not  yet  been  established  by 
recent  experiment,  but  are  calculated  from  others  eo  determined. 

FRESEMUS. 


APPENDIX. 


461 


TABLE  III. 

SPECIFIC     GRAVITY     OF     SOLIDS, 

Pure  water  at  60°  F=1.000 


Platinum         •>"'••'•• 

20  98 

Tin  

.     .     .  7  29 

Gold 

19  26 

Zinc 

7  03 

13  60 

Antimony     . 

.     .        6  70 

Lead 

,     .     11  45 

.     .     6.65 

Silver          .     .     . 

.     .     .  10.50 

.     .     .  6.00 

Bismuth.             . 

9  80 

.     .     5.80 

8  87 

Iodine      .               . 

495 

Cobalt 

8  54 

.     .     .     2  60 

Nickel             .     . 

.     .     .     8.28 

.     .     .  1.86 

8  00 

Sodum        ... 

.     .     .     0  97 

Iron                 . 

.    -.     .     7.80 

.     .     .  0.86 

TABLE  IV. 

SPECIFIC     GRAVITY      OF     LIQUIDS, 

Pure  water  at  60°  F=1.000 


Mercury 13.596 

Bromine  .  .  .  2.79  to  3.19 
Sulphuric  Acid .  .  .  .  1.800 
Nitric  Acid  1.515 


Ammonia  . 
Turpentine 
Alcohol .  . 
Ether  .  . 


0.870 
0.865 
0.800 
0.720 


TABLE  V. 

SPECIFIC     GRAVITY     OF     GASES. 

Dry  air  at  60°  F=1.000 


Chlorine 

454 

Oxygen 

1  109 

Nitrous  Oxide    .... 
Carbonic  Acid               . 

.525 
525 

Carbonic  Oxide 
Nitrogen               . 

.     .     .     0.970 
.     .     .  0  970 

Fluorine         

296 

.     .     .     0.069 

Hydrochloric  Ac.  gas  .     . 

.261 

Ammoniacal  gas 

.     .     .  0.589 

462 


APPENDIX. 


TABLE  VI. 

LINEAR  EXPANSION  OF  SOLIDS  ON  BEING  HEATED  FROM  32°  TO  212°  F. 


Zinc  (cast) 

expands     ~z%~% 

Iron                         expands 

_,_ 

Zinc  (sheet) 

3¥0 

Steel  (tempered) 

a!* 

Lead 

«         sir 

Steel  (untempered)     " 

J~2j 

Silver 

"         *i* 

Platinum                       " 

TiVT 

Copper 

"         yir 

Flint  Glass 

T2T¥ 

Gold 

*** 

Black  Marble 

2"83"1T 

TABLE  VIL 

SPECIFIC     HEAT. 

Water=1.000 


Alcohol 0.660 

Ether 0.520 

Nitric  Acid 0.442 

Oil  of  Turpentine  .     .     .     0.425 
Sulphuric  Acid    ....  0.833 

Carbon 0.241 

Common  Salt 0.225 

Lime 0.205 

Sulphur 0.202 

Glass    .  ,0.197 


Phosphorus 0.187 

Iron 0.113 

Zinc 0.099 

Arsenic 0.081 

Tin 0.056 

Iodine 0.054 

Silver 0.050 

Mercury 0.033 

Platinum 0.032 

Gold    ,  .     0.032 


TABLE  VIII. 

MELTING  POINTS  OF  SOLIDS. 


Cast  Iron              »ne/^  at     3479° 

Potassium              melts  at     154° 

Cobalt 

2800° 

Wax 

142° 

Silver 

2283° 

Spermaceti 

112° 

Gold 

2016° 

Phosphorus 

108° 

Copper 
Lead 

1996° 
612° 

Tallow 
Olive  Oil 

92° 

8G° 

Bismuth 

497° 

Ice 

32° 

Tin 

442° 

Oil  of  Turpentine 

—14° 

Sulphur 

226° 

Mercury 

—  39° 

Newton's  Alloy 

208° 

Liquid  Ammonia, 

—40° 

Sodium 

194° 

Ether 

i 

—47° 

APPENDIX. 


463 


TABLE  IX. 

BOILING  POINTS  OF  LIQUIDS. 


Mercury 

boils 

at 

662° 

Nitric  Acid 

boils  at 

248° 

Whale  Oil 

" 

it 

630° 

Water 

'      ' 

212° 

Sulphuric  Acid 

" 

«« 

620° 

Alcohol 

'      ' 

173° 

Sulphur 

" 

tt 

600° 

Bromine 

<      < 

116° 

Phosphorus 
Oil  of  Turpentine 

M 

it 

tt 

551° 
312° 

Ether 
Sulphurous  Acid 

'      ' 

96° 
14° 

TABLE  X. 

COMPOSITION  OF  HUMAN  BLOOD  ACCORDING  TO  LfiCANU. 


Water  

78.015 

Fibrin                                     .          .          .     . 

.     .       0  210 

6509 

13.300 

Crystallizable  fat    

0.243 

Oily  fat    

0.131 

Salts  of  the  alldlies      

0  837 

0.210 

0  545 

100.000 

TABLE  XL 

COMPOSITION  OF  COW'S  MILK. 


Water 873.0 

Casein,  and  a  little  albumen 48.2 

Butter 30.0 

Sugar  of  milk 43.9 

Phosphate  of  lime  with  a  little  chloride  of  calcium  ....  2.3 

Phosphate  of  iron  and  magnesia,  and  a  little  soda  ....  0.9 

Chlorides  of  sodium  and  potassium 1.7 

1000.00 


464  APPENDIX. 

TABLE  XII. 

RELATIVE   PROPORTIONS    OF    THE    SANGUIGENOUS    TO     THE    RESPIRATORY    CONSTI- 
TUENTS IN  DIFFERENT  KINDS  OF  FOOD. 


Sanguigenous. 

Respiratory. 

Cow's  milk         contains,  for     10 

30=  -S    8'8  fat  and 
(  10.4  milk  sugar 

Human  milk 

10 

40 

Horse  beans             " 

10 

22 

Peas 

10 

23 

Fat  mutton              " 

10 

27=11.25  fat 

Fat  pork 

10 

30=12.5     " 

Beef 

10 

17=7.08     " 

Veal 

10 

1=0.41     " 

Wheat  flour             " 

10 

46 

Oatmeal 

10 

50 

Rye  flour                 " 

10 

57 

Barley 

10 

57 

Potatoes  (white)     " 

10 

86 

Potatoes  (blue)       " 

10 

115 

Rice 

10 

123 

Buckwheat             " 

10 

130 

Starch  is  the  principal  constituent  of  respiratory  food  in  the  sub- 
stances mentioned  in  the  table.  When  sugar  and  fat  take  its  place,  the 
fact  is  separately  indicated,  while  their  equivalent  in  starch  is  given 
in  the  principal  column  for  convenience  of  comparison.  The  above 
table  is  taken  from  Liebig's  Letters  on  Chemistry. 

TABLE  XIIL 

PER  CENT  BY  MEASURE  OF  ALCOHOL  IN  SPIRITOUS  LIQUORS  AT  62°  F. 


Rum                           contains 

72  to  77  per  cent. 

Cognac                             " 
Whiskey 

50   "    54 
59 

Geneva 

50 

Port            wine             " 

21  to  23 

Sherry 

15    "   25 

Madeira         "                 " 

18    "   22 

Malmsey        "                 " 

16 

Claret            "                " 

9  to  15 

Burgundy      "                " 

7    "    13 

Rhenish 

8    "    13 

Moselle 

8    "     9 

Tokay 

9 

Champagne  " 

5  to  15         " 

APPENDIX. 


465 


TABLE  XIV. 

HOMOLOGOUS   SERIES    OF   ORGANIC   ACIDS. 


1.  Formic  .... 

CaHaCM        16.  Ethalic    . 

.       .      .       C32H3204 

2.  Acetic    .... 

CiHiOi 

17.  Stearic    . 

.      .       .       C34H34O4 

3.  Propiouic    .     .    . 

CSH604 

18.  Bassic     . 

.      .      .       C3SH3&O4 

4.  Butyric  .... 

CsHsOi 

19. 

5.  Valeric    .... 

CicHicCM 

20. 

6.  Caproic    .... 

Cl2Hl204 

21. 

7.  Enanthylic    .    .     . 

Cl4Hl404 

22.  Behenic 

.      .      .      C44H4404 

8.  Caprylic  .... 

CieHieO4 

23. 

9.  Pelargonic    .     .     . 

CisHisCh 

24. 

10.  Capric     .... 

CsoHsoCh 

25. 

11.  Margaritic    .     .    . 

C22H2204 

26. 

12.  Laurie     .... 

C24H2104 

27.  Cerotic  . 

.      .       .      C54H3404 

13.  Cocinic    .... 

C26H2S04 

28. 

14.  Myristic  .... 

GssHttOl 

29. 

15.  Benic       .... 

C3oHscO4 

30.  Melissic  . 

.    .    .    CsoHsi04 

TABLE  XV. 

COMPOSITION    OF   THE   ASHES    OF   COMMON    CROPS. 


ndian 
Corn. 

Wheat 

Wheat 
Straw. 

Rye. 

Oats. 

Pota- 
toes. 

Tur- 
nips. 

Hay. 

Carbonic  acid, 

trace. 

10-4 

Sulphuric  acid, 

0-5 

i-o 

i-o 

1-5 

10-5 

7-1 

13.6 

2-7 

Phosphoric  acid, 

49-2 

47-0 

31 

47-3 

43-8 

11-3 

7-6 

6-0 

Chlorine,      .     . 

0-3 

:race. 

0-6 

0-3 

2-7 

3-5 

2-6 

0-1 

2'9 

85 

2-9 

4-9 

1*8 

13-6 

22  -9 

Magnesia,     .     . 

17-5 

15'9 

5-0 

10-1 

9-9 

5-4 

5-3 

5-7 

Potash,      .     .     . 
Soda,  .... 

23-2 

3-8 

29-5 
trace. 

7'2 
0-3 

32-8 
4-4 

j-  27-2 

51-5 
trace. 

42-0 
5-2 

18-2 
2-3 

Silica,   .... 

0-8 

1-3 

67-6 

0-2 

2-7 

8-6 

7-9 

37-9 

Iron,    .... 

0.1 

trace. 

1-0 

0-8 

0-4 

0-5 

1-3 

1-7 

Charcoal  in  ash,  ) 
and  loss,     .      ) 

4'5 

2'4 

5-7 

0-3 

0-7 

lOO'O 

100-0 

lOO'O 

lOO'O 

lOO'O 

100-0 

100-0 

100-0 

Lbs.  of  material  } 

6000 

12500 

1000 

requir'd  to  yield  > 
100  Ibs.  of  ashes.  j 

10000 

5000 

2000 

5000 

2500 

to 

13000 

to 
20000 

to 

2000 

20' 


466 


APPENDIX. 

TABLE  XVI. 

SOLUBILITY  OF  SUBSTANCES 


KG 

NaO 

NH40 

BaO 

SrC 

CaO 

MgC 

AbO 

MnO 

FeO 

NIC 

1 

1 

1 

1 

1 

12 

2 

2 

2 

2 

2 

s 

1 

1 

1 

1 

1 

i2 

2 

2 

2 

Cl 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

I 

1 

1 

1 

1 

1 

1 

1 

1 

1 

SO3 

1 

1 

1 

3 

3 

1*8 

1 

1 

1 

1 

1 

NOo 

I 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

POs 

1 

1 

1 

2 

2 

2 

2 

2 

2 

2 

COa 

1 

1 

1 

2 

2 

2 

2 

2 

2 

2 

CaOs 

1 

1 

1 

2 

2 

2 

2 

2 

2 

i  2 

BOa 

1 

1 

1 

2 

2 

2 

2 

2 

2 

2 

2 

A 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

"T 

1 

1 

1 

2 

2 

2 

12 

1 

i2 

i2 

AsOs 

1 

1 

1 

2 

2 

2 

2 

2 

2 

2 

2 

AsOa 

1 

1 

1 

2 

2 

2 

2 

2 

CrOs 

1 

1 

1 

2 

2 

2 

1 

2 

1 

2 

EXPLANATION  OF  THE  TABLE. 

To  ascertain  the  solubility  or  insolubility  of  a  salt  from 
tbe  above  table,  its  acid  is  sought  in  the  left  hand  column, 
and  its  base  in  the  upper  line.  The  square,  which  is  in  line 


APPENDIX. 


467 


TABLE  XVI.— (CONTINUED.) 
IN  WATER  AM)  ACIDS. 


ZnO 

PbO 

SnO 

SnO 

BiOa 

CuO 

Hg20 

HgO 

AgC 

PtO 

SbO 

2 

2 

2 

23 

2 

2 

2 

2 

2 

2 

s 

2 

2 

2 

3 

3 

2 

Cl 

1 

11 

1 

1 

1 

1 

2 

1 

3 

1 

I 

1 

2 

2 

1 

2 

2 

3 

SO3 

1 

2 

1 

1 

1 

i2 

1 

1   2 

1 

2 

NOo 

1 

1 

1 

1 

1 

1 

1 

1 

POs 

2 

2 

2 

2 

2 

2 

CO2 

2 

2 

2 

2 

2 

2 

2 

CaOs 

2 

2 

2 

1 

2 

2 

2 

2 

2 

12 

BOs 

2 

2 

2 

2 

2 

1 

A 

1 

1 

1 

1 

1 

1 

12 

1 

1 

1 

f 

2 

2 

12 

2 

1 

i2 

2 

2 

1 

AsOs 

2 

2 

2 

2 

2 

2 

2 

AsOs 

2 

2 

2 

2 

2 

2 

CrOa 

1 

2 

2 

2 

2 

2 

i2 

2 

2 

with  both,  contains  the  desired  information.  The  numeral 
1,  indicates  solubility  in  water ;  2,  solubility  in  either  nitric 
or  hydrochloric  acid,  and  3,  insolubility  in  either.  The 
smaller  numerals  indicate  a  low  degree  of  solubility. 


INDEX. 


Acetic  Acid,  372. 
Acid,  Arsenious,  180. 

Antidote  to,  185. 
Marsh's  Test  for,  181. 
Poisonous  properties 

of,  181. 
Boracic,  197. 
Carbonic,  189. 
Hydrochloric,  210. 

Action  of,  on  Metals, 

211. 

Hydrocyanic,  374. 
Hydrofluoric,  212. 
Hydrosulphuric,  214. 
Muriatic,  210. 
Nitric,  173. 
Oxalic,  378. 
Prussic,  377. 
Stearic,  420. 
Sulphuric,  162. 
Sulphurous,  167. 
Stannic,  285. 
Tannic,  373. 

Acids.  Formation  of,  136. 
Organic,  372. 
Properties  of,  137. 
Affinity,  Relation  of  cohesion  and, 

277. 
Air,  Analysis  of  the,  172 

Proportional   Composition  of 
the,  173. 


TJnsaturated,  71. 
Albumen,  Vegetable,  389. 
Alcohol,  362. 
Aldehyde,   Conversion  of  Alcohol 

into,  370. 

Alkali,  Volatile,  218. 
Alkalies,  The,  286. 

Effects  of,  on  Wood,  353. 

Vegetable,  395, 
Alkaloids, 
Alloys,  272 
Alum,  307. 

Different  kinds  of,  308. 
Alumina,  292. 
Aluminium,  238. 
Amalgams,  261. 
Ammonia,  216. 

Carbonate  of,  815. 

Nitrate  of,  311. 
Ammonium,  235. 

Oxide  of,  290. 
Analysis,  Chemical,  332. 

Organic,  430. 
Anastatic  printing,  331. 
Animal  Body,  Chemical  changes  in 
the,  424. 

Heat,  424. 

Tissues,  Changes  of,  426. 
Antimony,  251. 

Apparatus  for  silvering  and  gild- 
ing, 107. 

Aqua  Regia,  212. 
Arsenic,  179. 


INDEX. 


469 


Arsenic,  Eaters  of  Austria,  185. 

Marsh's  Test  for,  181. 
Artificial  Essences,  382. 
Ashes,  Effect  of,  on  Soils,  407. 
Asphaltum,  386. 
Assay  of  Gold,  269. 

Silver,  265. 

Atmosphere,  Elastic  Force  of  the, 
78. 

Quantity  of  vapor  in  the,  71. 

Weight  of  the,  77. 
Atomic  Weights,  Table  of,  App. 
Atoms  and  Attraction,  1 1. 
Attraction,  Chemical,  12. 

Distance  of,  13. 

of  Cohesion,  12. 

of  Gravitation,  12. 


B. 

Barium,  237. 
Barometer  Guage.  90. 
Baryta,  Sulphate  of,  307. 
Bases,  Organic,  395. 

Properties  of,  137. 
Batteries,  Different  kinds  of,  114. 
Batten7,  Decomposition  in  the,  112. 
Bismuth,  253. 
Bleaching,  by  Oxygen,  147. 
Sulphur,  160. 

Powder,  298. 
Blood,  Composition  of  the,  415. 

Changes  in  the,  424. 

Color  of  the,  425. 

Table  of  the   Composition  of 
the,  App. 

Transformation  of  the,  414. 
Blowpipe,  227. 

Oxhydrogen,  229. 
Boiling,  77-80! 

Disappearance  of  Heat  in,  81. 

Effect  of  Depth  on,  83. 
Height  on,  83. 

Expansion  in,  81. 

Point,  Artificial  Change  of,  84. 
Height  measured  by,  83. 
Bones,  416. 
Boracic  Acid,  197. 
Borates,  323. 
Boron,  197. 


Bread,  Raising  of,  393. 
Bromine,  158. 
Burning  Fluid,  380. 

46. 

of  Ice,  47. 


C. 

Calcium,  237. 

Oxide  of,  290. 
Camphors,  383. 
Caoutchouc,  387. 
Carbon,  185. 

Combustion  of,  188. 
Carbonates,  313. 
Carbonic  Acid,  189. 

Oxide,  194. 

Carburetted  Hydrogen,  Heavy,222. 
Light,  221. 
Casein,  389. 

Cellars  warmed  by  Ice,  65. 
Cement,  Hydraulic,  292. 
Chamelion  Mineral,  326. 
Charcoal,  Combustion  of,  in  Oxy- 
gen, 145. 

Decoloring  effects  of,  188. 

Preparation  of,  186-349. 

Preservative  properties  of,  187. 

Purifying  properties  of,  187. 

Reduction  of  Ores  by,  188. 
Cheese,  423. 
Chemical  Analysis,  332. 
Chemistry,  Organic,  General  views 

of,  335. 
Chloride  of  Lime,  298. 

Sodium,  296. 
Chlorides,  294. 
Chlorine,  149. 

a  Disinfectant,  154. 

Bleaching  by,  153. 

Compounds  of,  with  Oxygen, 
156. 

Relations  to  Animal  Life,  155. 

Resemblance  to  Oxygen,  155 

Test  for,  301. 
Chloroform,  371. 
Chromates,  325. 
Chromium,  245. 
Circulation  of  Matter,  433. 
Clay,  320. 


470 


INDEX. 


Cloth,  Incombustible,  352. 
Coal,  Anthracite,  851. 

Oils  from,  355. 
Cobalt,  245. 
Cohesion,  12. 

Relation  of,  and  Affinity,  277. 
Cold,  Definition  of,  27. 

Extreme,  how  measured,  59. 

Supposed  Radiation  of,  45. 

Water,  Lightness  of,  55. 
Collodion,  356. 

Color,  Change  of,  by  Touch,  301. 
Coloring  Matters,  396. 
Combustion,  Definition  of,  145. 

under  Water,  178. 
Composts,  407. 
Compound  Blowpipe,  229. 

Circuit,  Decomposition  by  the, 
115. 

Galvanic  Circuit,  114. 

Radicals,  340. 
Concave  Lens,  Action  of,  22. 

Mirrors,  Theory  of,  19. 
Conducting   Power,  Simple    Test 

of,  35. 

Copper,  254. 

Counterfeiting,  Prevention  of,  331. 
Crystal  Forms,  Systems  of,  281. 

Glass,  321. 
Crystallization,  208. 
Culinary  Paradox,  84. 
Cupellation,  263. 
Cyanides,  374. 
Cyanogen,  374. 


D. 

Daguerreotype,  The,  327. 
Davy's  Safety  Lamp,  222. 
Decay,  Preventives  of,  352. 
Definite  Proportions,  Law  of,  134. 
Dew,  75. 

Absence  of,  on  Polished  Sur- 
faces, 45. 

Artificial  prevention  of,  44. 

Formation  of,  44. 

Point,  74. 

how  to  find  the,  74. 
Distillation,  97. 


Dyeing,  397. 
Dyes,  Mineral,  399. 


E. 

Earth,  Cooling  of  the,  43. 
Earthen-ware,  322. 
Effervescent  Drinks,  191. 
Elastic  Force  of  Vapors,  89 
Electric  Light,  111. 
Electricity  and  Magnetism,  99. 

Conduction  of,  103. 

Decomposition   of  water  by. 
105. 

Frictional,  102. 

Galvanic,  103. 

Quantity  of,  in  Matter,  104. 

Theory  of,  102. 
Electrodes,  103. 

Elements,  Electrical  Relations"of 
138. 

Number  of,  11. 

Table  of,  App. 
Empyreumatic  Oils,  382. 
Enamel,  322. 
Engine,  The  Steam,  91. 
Equivalents,  Chemical,  134 

Table  of,  App. 
Essences,  Artificial,  382. 
Essentials  Oils,  379. 
Etching  on  Glass,  213. 
Ether,  Conversion  of  Alcohol  into, 

368. 

Ethyl,  Production  of,  369. 
Evaporation,  Economy  in,  97. 

Effect  of  Wind  on,  70. 

Freezing  by,  68. 

Protection  from  Heat  by,  68. 
Expansion,  50. 

Fracture  of  Glass  Vessels  by, 
53. 

Law  of,  for  Gases,  57. 

Lifting  Walls  by,  52. 

of  Cold  Water  by  Cold,  54. 
Gases,  56. 
Liquids,  54-56. 
Solids,  51. 
Wood  and  Marble,  53. 


INfJEX. 


471 


F. 

Fats,  Composition  of,  419. 

Separation  of,  in  Oil,  419. 

Tallow    and 
Lard,  420. 
Fermentation,  391. 
Ferrocyanides,  376. 
Fibre,  Woody,  349. 
Filtration,  207. 
Fire  by  Compression,  50. 

on  Water,  36. 

Proof  Safes,  35. 
Flame,  225. 

Effect  of,  on  Metals,  226. 
Flesh,  417. 
Fluorides,  302. 
Fluorine,  158. 
Fogs,  72. 

Food  and  Temperature,  Kelations 
of,  426. 

Proportions  of,  429. 

Transformation  of  the,  414. 

Varieties  of,  428. 
Freezing,  64. 

by  Evaporation,  68. 

Mixtures,  63. 
Fusel  Oil,  372. 


O. 

Galvanic   Coil,   Motion  of  a  sus- 
pended, 120. 
Polarity  of,  imparted  to 

Metals.  122. 
Polarity  of  the,  119. 
The,  a  magnetic  needle, 

121. 

Coils,  Mutual  Action  of,  121. 
Current,   Heating   Effects   of 

the,  111. 
Magnetic  Effects  of  the, 

119. 
Galvanism,  Discovery  of,  127. 

Physiological  Effects  of,  126. 
Gas  from  Wood,  225. 

Illuminating,  223-349. 
Gastric  Juice,  The,  414. 
Gelatine,  418. 


ermination,  345. 
Gilding,  270. 

Galvanic,  107. 
lass,  Colored,  322. 

Crystal,  321. 

cut  by  Hot  Wire,  53. 

Etching  on,  213. 

Soluble,  320. 

Staining,  294. 

Window,  320. 
Glauber's  Salt,  306. 
Glycerine,  420. 
Gold,  267. 
Gravitation,  12. 
Green,  Chrome,  326. 

Mineral,  400. 
Guano,  407. 
Gum  from  Wood,  357. 

Resins,  387. 
Gun  Cotton,  355. 
Gunpowder,  311. 
Gutta  Percha,  388. 
Gypsum,  305. 


II. 

Heat,  Absorption  of,  42. 

Analysis  of,  46. 

Animal,  424. 

Capacity  for,  49. 

Changes  effected  by,  48. 

Communication  of,  30. 

Conduction  of,  30. 

Convection  of,  37. 

Disappearance  of,  in  Boiling, 
81. 

Melting,  62. 
Vapors,  67. 

Extreme,  how  measured,  60. 

Latent,  65. 

Nature  of,  25. 

of  Chemical  Action  and  Elec- 
tricity, 29. 
the  Fixed  Stars,  29. 

Protection  from,  by  evapora- 
tion, 68. 

Quantity  of,  given  out  by  tha 
Sun,  28. 

Radiation  of,  39. 


472 


INDEX. 


Heat,  Rays  of,  45. 

Effect  of  different,  47. 
Reflection  of,  41. 
Refraction  of,  45. 
Relation  of,  to  Density,  49. 
Specific,  48. 

the  Ocean  a  Reservoir  of,  50. 
Theories  of,  25. 
Transmission  of,  41. 
Heavy     Carburetted     Hydrogen, 

222. 

Hides,  Tanning,  418. 
Homologous  Series,  341. 

Table   of    the,   of 
Organic  Acids, 

App. 

Humus,  Production  of,  351. 
Hydrates,  286. 
Hydraulic  Cement,  292. 
Hydrochloric  Acid,  210. 
Hydrocyanic  Acid,  374. 
Hydrofluoric  Acid,  212. 
Hydrogen,  197. 

Phosphuretted,  219. 
Sulphuretted,  214. 


I. 


Ice  in  the  Tropics,  43. 
Ignition  by  Lime,  291. 
Illuminating  Gas,  223. 
Incrustations  in  Boilers,  316. 
Indigo,  396. 

Induction,  Magnetic,  without  Con- 
tact, 101. 
Ink,  Writing,  373. 
Intensity  of  Electricity,  Meaning 

of,  115 
Iodine,  156. 
Iron,  240. 

Combustion  of,  in  Oxygen, 143. 
Isomorphism,  284. 


EN 

Lamp  Black,  Preparation  of,  187. 
Latent  Heat,  Proof  that  Boiling  is 
effected  by,  96. 


Latent  Heat,  Quantity  of,  in  Steam, 

96. 

Sum  of,  and  Sensible  Heat 
always  the  same,  96. 
Laughing  Gas,  311. 
Lead,  256. 

Chromate  of,  325. 
Light,  15. 

Analysis  of,  22. 

Chemical  Action  of,  15-329. 

Laws  of,  17. 

Medium,  Definition  of,  17. 

Ray,  Definition  of,  17. 

Reflection  of,  18. 

Refraction  of,  20. 

Theories  of,  15. 

Light  Carburetted  Hydrogen,  221. 
Lime,  Action  of,  in  Soils,  405. 

Ignition  by,  291. 

Nitrate  of,  309. 

Sulphate  of,  305. 
Liniments,  422. 
Liquefaction,  61. 

Liquids,  Conversion  of  vapors  into, 
95. 

Nonconductors  of  Heat,  36. 
Logwood,  397. 

Dyeing  with,  399. 
Lunar  Caustic,  312. 


Madder,  397. 
Magnesium,  237. 
Magnet,  Artificial,  99. 
Magnetic  Induction  without  Con- 
tact, 101. 

Needle,  99. 

Telegraph,  124. 

Magnets,    Attraction    of,  for  each 
other,  100. 

Native,  99. 

Magnetism,   Electrical  Theory  of, 
126. 

Induced,  100. 
Mahomet's  Coffin,  119. 
Manganates,  326. 
Manganese,  239. 
Marble,  Artificial,  317. 
Marsh's  Test  for  Arsenic,  181. 


INDEX. 


473 


Matches,  Friction,  178. 
Mercury,  259. 

Quantity  of,  the  Air  can   Sus 

tain,  80. 
Metals,  231. 

Classification  of,  231. 
Deposition  of,  by  Electricity, 

106. 

Effect  of  flame  on,  106. 
Milk,  422. 

Solid,  423. 

Table  of  the  Composition  of, 
Cow's,  A  pp. 
Human,  App. 
Mineral  Dyes,  399. 
Moisture,  Deposition  of,  70. 
Molasses,  361. 
Mordants,  398. 

Multiple  Proportions,  Laws  of,  134. 
Muriatic  Acid,  210. 

Effect  of,  on  Wood,  354. 


Nickel,  246. 
Nitrate  of  Silver,  312. 
Nitrates,  309. 
Nitre,  310. 
Nitric  Acid,  173. 

Effects  of,  on  Wood,  352. 
Nitrogen,  169. 
Nutrition,  Vegetable,  346. 


O. 

Oil  of  Vitriol,  Manufacture  of,  163. 
Oils,  Empyreumatic,  382. 

Essential,  379. 

from  Coal,  355. 

Olefiant  Gas,  Conversion  of  Alco- 
hol into,  369. 
Organic  Acids,  372. 

Analysis,  430. 

Bases,  395. 

Chemistry,  General  Views  of, 

335. 

Oxalic  Acid,  378. 
Oxides,  285 


Oxides,  Formation  of,  136. 

Names  of,  135. 

reduced   by  Carbonic  Oxide, 
195. 

Uses  of,  293. 
Oxygen,  141. 

a  Purveyor  for  Plants,  147. 

Bleaching  by,  147. 

Compounds  of,  with  Chlorine, 

156. 

Oxhydrogen  Blowpipe,  229. 
Ozone,  148. 


P. 

Peat,  350. 
Petroleum,  386. 
Phosphates,  317. 
Phosphorescence,  177. 
Phosphorus,  176. 

Combustion  of,  by  Nitric  Acid, 
176. 

Combustion  of,  in  Oxygen,  144. 
Phosphuretted  Hydrogen,  219. 
Photographs,  329. 
Plants,  Constituents  of,  348. 

Relation  of,  to  the  Soil,  402. 
Plaster,  Aluminated,  306. 

of  Paris,  305. 
Platinum,  271. 
Porcelain  Painting,  323. 
Potassa,  287. 

Carbonate  of,  314. 

Nitrate  of,  310. 
Potassium,  233. 

Cyanide  of,  375. 
Precipitation,  207-275. 
Pressure,  Actual,  in  different  En- 
gines, 90. 

of  the  Atmosphere,  79. 

The  Exact  Relation  of  Temper- 
ature to,  88. 
Printing,  Anastatic,  331. 

Calico,  400. 
Prism,  construction  of,  21. 

Effect  of,  on  Rays,  21. 
Prussic  Acid,  377. 
Putrefaction,  390. 


474 


INDEX. 


Quantity  of  Electricity,  Meaning 
of,  115. 


R. 

Radiation  of  Heat,  39. 

Color  not  effected  by,  40. 

Polish  unfavorable  to,  40. 

Proportion  of,  to  Temperature; 

39. 

Radicals,  Compound,  340. 
Rays,  Heat  and  Chemical,  45. 
Refraction  of  Heat,  45. 

Light,  20.  ^ 

Refrigerators,  Construction  of,   34. 
Resins,  383. 

Gum,  387. 
Respiration,  425. 
Roots,  Office  of  the,  347. 
Rosin  Oil,  386. 

Soap,  385. 


S. 

Safety  Lamp,  Davy's,  222. 
Sal- Ammoniac,  218. 

Volatile,  315. 
Salt,  Common,  296. 

Decomposition   of  a,  by  Gal- 
vanism, 117. 

Glauber's,  306. 
Saltpetre,  310. 
Salts,  274. 

Formation  of,  136. 

Names  of,  135. 
Sealing  Wax,  385. 
Shot,  Manufacture  of,  259. 
Silicates,  319. 
Silicon,  196. 
Silver,  262. 

Assay,  265. 

Nitrate  of,  312. 

obtained  from  Lead,  263. 
Silvering,  Galvanic,  107. 
Sizing  for  Paper,  875. 
Skin,"  Tendons  and  Ligiments,  417. 


Soaps,  421. 

Properties  of,  422. 
Soda,  Carbonate  of,  314. 

Sulphate  of,  306. 
Sodium,  235. 

Chloride  of,  296. 
Soils,  402. 
Soldering,  324. 
Soluble  Glass,  320. 
Solution,  206-274. 

Effect  of,  on  Chemical  Affinity, 

138. 

Spirituous  Liquors,  366. 
Stalactites,  317. 
Stalagmites,  317. 
Starch,  357. 
Starvation,  427. 
Steam  Boilers,  86. 

Elastic  Force  of,  87. 

Engine,  91. 

Guages,  90. 

Heating  Houses  by,  95. 
•     Safety  Valve,  91. 

Water  Heated  by,  95. 
Stearic  Acid.  420. 
Steel,  243. 

Permanent  Magnetism  of,  123. 

Tempering,  244. 
Strontium,  237. 
Substitution,  Equivalent,  339. 
Substitutions,  343. 
Sugar,  Boiling  in  Vacuo,  85. 

Cane,  360. 

Grape,  359. 

from  Starch,  358. 
Wood,  356. 

Manufacturing,   Use    of   Sul- 
phurous Acid 

in,  159. 

Sulphates,  305. 
Sulphur,  159. 

Liver  of,  303. 

Milk  of,  304. 
Sulphurets,  302. 
Sulphuretted  Hydrogen,  214. 
Sulphuric  Acid,  16.2. 

Effect  of,  on  Wood,  352. 
Sulphurous  Acid,  167. 
Superphosphate  of  lime,  318-411. 


INDEX. 


475 


Symbols,  Calculation   of  Weights 

from,  133. 
Explanation  of,  132. 

T. 

Tannic  Acid,  373. 
Tanning,  Hides,  418. 
Tar,  Wood,  353. 
Tartar,  367. 

Tea  Kettle,  Singing  of  the,  86. 
Temperature  and  Food,  Relations 
of,  426. 

Equilibrium  of,  42. 

The   exact  Relation  of  Pres- 
sure to,  88. 
Thermometers,  Graduation  of,  58. 

Manufacture  of,  57. 

The  Air,  60. 
Tin,  248. 

Tissues,  Repair  of  the,  428. 
Types,  Chemical,  339. 


T. 

Vaporization,  66. 

Vapor,  Capacity  of  the  Air  for,  75. 
Quantity  of,    in  the    Atmos- 
phere, 69. 
Quantity  of   water  the    Air 

may  contain  as,  69. 
Relations  of  Air  and,  69. 
Vapors,  Conversion  of  Liquids  in- 
to, 95. 
Density  of,  66. 

depends  on  Tem- 
perature, 67. 
Elasticity  of,  66. 
Formation  of,  66. 
Transparent,  66. 
Varnishes,  384. 
Vegetable  Chemistry,  345. 
Vinegar,   Conversion    of  Alcohol 

into,  370. 

Process   of  Manufacture,  371. 
Wood,  353. 


Voltaic  Pile,  118. 
Vulcanized  Rubber,  387. 


W. 

"Water,  Action  of,  on  Lead,  257. 
Affinity  of  Potassa  for,  288. 
Capacity  of  Air  for,  increased 

by  Heat,  70. 
Chemical     Combinations    of, 

208. 

Decomposition  of,  by  Electri- 
city, 105-115. 
Hammer,  85. 
heated  by  Steam,  95. 
Proof  of  the  Composition   of, 

203-204. 

Quantity  of,  the  Air  may  con- 
tain as  Vapor,  69. 
Quantity  of,  the  Pressure  of 
the  Air  will  Sustain, 

79. 

Sea,  297. 
Theory  of  the  Decomposition 

of,  105.    \ 
Welding  Iron,  243. 
White  Rotten  Wood,  351. 
Window  Glass,  320. 
Wines,  366. 
Wood,  349. 

Charred  by  Sulphuric  Acid, 

167. 

Conversion  into  Gum,  357. 
Sugar,  356. 


Y. 

Yeast,  391, 

Powders,  393. 
Yellow,  Chrome,  325-400. 


Z. 


Zinc,  246. 


476  APPARATUS  AND  MATERIALS. 


LIST  OP    CHEMICALS    AND    APPARATUS   REQUIRED    FOR    THE  EX- 
PERIMENTS  DESCRIBED  IN  THIS  WORK. 

1  lb.  Black  Oxide  of  Manganese 

J  "  Bleaching  Powders. 

£  "  Chlorate  of  Potassa. 

J  «  Alum. 

£  "  Sulphur. 

J  "  Common  Caustic  Potash,  in  Sticks. 

I  "  Acetate  of  Lead,  (Sugar  of  Lead.) 

1  "  Sulphate  of  Copper,  (Blue  Vitriol.) 

J  "  Carbonate  of  Ammonia,  (Sal  Volatile.) 

2  oz.  Bichromate  of  Potash. 
2  "   Bone  Black. 

2  "  Sulphuret  of  Iron. 

2  "  Nitrate  of  Potash,  (Salt  Petre.) 

"  Chloride  of  Ammonium,  (Sal  Ammoniac.) 

"  Yellow  Prussiate  of  Potash. 

"  Cyanide  of  Potassium. 

14  Oxalic  Acid. 

"  Ground  Nut  Galls. 
1  "  Phosphorus. 
1  "  Fluor  Spar. 
1   "  Borax. 

1  "  Chloride  of  Barium. 
1  "  Chloride  of  Strontium. 

1  "  Chloride  of  Mercury,  (Corrosive  Sublimate.) 
1  "  Beeswax. 
1  "  Metallic  Antimony 
1  "  Block  Tin. 

1  "  Bismuth. 

2  ««  Mercury,  (Quicksilver.) 

1  "  Arsenious  Acid,  (Ratsbane.) 


APPARATUS  AND  MATERIALS.  477 

\  oz.  Tartar  Emetic. 

\  "  Iodide  of  Potassium. 

J  "  Iodine. 

£  "  Potassium. 

J  "  Solution  of  Chloride  of  Platinum. 

1  Glass,  (4  oz.)  Spirit  Lamp. 

Fine  platinum  foil  and  wire. 

1  doz.  assorted  test-tubes. 

^  sheet  blue  Litmus  Paper. 

\     "       red  Litmus  Paper. 

Fine  Iron  Wire. 

*  Sheet  Zinc. 

*  Sheet  Copper. 

*  Sulphuric  Acid,  (Oil  of  Vitriol.) 

*  Hydrochloric  Acid,  (Muriatic  Acid.) 

*  Nitric  Acid,  (aqua  fortis.) 

*  Alcohol. 

*  Ether. 

*  Clay  Pipes  and  Vials. 

*  Bowls,  Tumblers,  &c. 

*  Not  contained  in  the  box  of  apparatus  and  materials  put  up  to 
accompany  this  work. 


XiVKKSITY  OF  CALIFORNIA  LIBRARY 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 


DEC 


NOV    3   1915 


JUL  2 
MAY  IB 


JAN 


30m-6,'14 


